info that might help (before you ask, yeah the LT1 is very similar)
L-98 Engine Start Sequence
knowing whats going on and WHY can help
http://members.shaw.ca/corvette86/Component Location View 86.pdf
When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.
Fuel Rail Pressurization:
When you first turn the key to the â€œonâ€ position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail
Initial Crank Action:
If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.
Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driverâ€™s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).
The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.
If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).
The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you canâ€™t make at least 4 PSI oil pressure. This is a â€œlimp home modeâ€ feature put in place to allow for a fuel pump relay failure).
The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)
Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will â€œcatchâ€.
When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).
The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.
If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.
The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.
Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensorâ€™s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more â€œon timeâ€ or less â€œon timeâ€) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.
Note that prolonged idling can force the computer back into open loop mode.
Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.
Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.
If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.
A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.
Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).
A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).
Theory of Operation
As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.
Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.
It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.
MAF Operating Conditions
The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.
There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.
The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.
Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.
A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).
Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.
Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.
A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.
this flow chart might help
AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.
The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.
The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.
The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.
Welcome to C4 vette codes it is very ....repeat very
important that if you are not savvy of working on your
vette ...you would be better off - taking your car to a
dealership for repairs on your trouble codes.
However if you feel that you want to dive right in ..than you
have come to the right place.First locate your car's alcl
this component is located just below the instrument panel and
to the left of the center console. Remove the plastic cover
the first two slots to your right are the A & B slots for a drawing of
the alcl module's picture is added below.
The A slot is the diagnostic slot and the B slot is the ground
slot. insert the computer key into these slots (with the engine
off) this is very important...now only put the ignition key
to on ( not start !!!) the check engine light will display a
code 12 which is one flash followed by two flashes.
this code will be flashed three times ..followed by the
trouble code stored in your car's computer.
what ever the code is it will be flashed three times.
have a paper and pencil ready and write down the
code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
please remember that if you have the computer key installed
in the alcl and you start the engine ( you will ruin the engine's computer
only put the ignition to on (not to start)
If you should get a check engine soon display.. you can use
the above procedure and codes to buy the right part
or at the very least to keep from getting taken for a ride
and be made to pay hight prices for some inexpensive
module that you could have installed yourself.
You never ask a barber if you need a haircut ..
so you have to be on guard they will see you comming
a mile away.
If your engine displays a trouble code ... your engine will
go into limp mode ..it will still run but very poorly.
you might be able to reset the computer if it will not start
( just to get home ) by disconnecting both battery cables
and re-installing them ...this is not recommended ..but if
you are stranded it might help unitl you get your car home
or to a repair shop..good luck
1985 TO 1991:
Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.
ECM CODES 1992 TO 1993:
Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.
CODES 1994 TO 1996:
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.
_________________you really can,t be effectively at playing mr-fix-it with out the correct tools
See the DTC page for P0.. (generic) codes and Glossary for terms and acronyms..
P1031 H02 Sensor Heater Control Circuit Problem
P1106 intermittent high or low Voltage in circuit of sensor MAP
P1107 MAP Sensor Circuit Intermittent Voltage Low
P1108 BARO to MAP Signal Circuit Comparison Too High
P1111 IAT Sensor Circuit Intermittent Voltage High
P1112 IAT Sensor Circuit Intermittent Voltage Low (except Catera)
P1112 Intake Plenum Switchover Valve Control (Catera)
P1113 Intake Resonance Switchover Valve Control
P1114 ECT Sensor Circuit Intermittent Voltage Low
P1115 ECT Sensor Circuit Intermittent Voltage High
P1120 Throttle Positioning Sensor 1 Circuit
P1121 Throttle Positioning Sensor 1,2 Circuit Performance/ Fuel Injector Secondary System Circuit Low
P1122 TPS Circuit Intermittent Voltage Low
P1125 APP System
P1133 HO2S/O2S Insufficient Switching Sensor 1 Or Bank 1 Sensor1
P1134 HO2S Transition Time Ratio Bank 1 Sensor 1
P1137 HO2 Sensor Low Voltage During Power Enrichment
P1138 HO2 Sensor High Voltage During Decel Fuel Cutoff
P1139 HO2S Insufficient Switching Bank 1 Sensor 2
P1140 HO2S Transition Time Ratio Bank 1 Sensor 2
P1141 HO2 Sensor Heater Control Circuit (Bank 1 Sensor 2)
P1153 HO2S Insufficient Switching Bank 2 Sensor 1
P1154 HO2S Transition Time Ratio Bank 2 Sensor 1
P1158 HO2 Sensor Shift Rich (Bank 2 Sensor 2)/ Engine Metal Over-Temperature Protection
P1161 HO2 Sensor Heater Control Circuit (Bank 2 Sensor 2)
P1171 Fuel System Lean During Acceleration
P1187 Engine Oil Temperature Sensor Circuit Voltage Low (except 1997 Corvette)
P1187 Engine Oil Pressure Sensor Circuit Voltage Low (1997 Corvette)
P1188 Engine Oil Temperature Sensor Circuit Voltage High (except 1997 Corvette)
P1188 Engine Oil Pressure Sensor Circuit Voltage High (1997 Corvette)
P1189 Engine Oil Pressure Switch Circuit
P1200 Injector Control Circuit
P1214 Injection Pump Timing Offset
P1215 Generator Driver Circuit
P1216 Fuel Solenoid Response Time Too Short
P1217 Fuel Solenoid Response Time Too Long
P1218 Injection Pump Calibration Circuit
P1220 Throttle Position (TP) Sensor 2 Circuit Fault
P1221 TP Sensor 1, 2 Performance
P1222 Injector Control Circuit Intermittent
P1250 Early Fuel Evaporative (EFE) Heater Circuit
P1257 Boost Control Condition/Supercharge System Overboost
P1260 Fuel Pump Speed Relay Control Circuit
P1271 Accelerator Pedal Position Sensor 1-2 Correlation
P1272 Accelerator Pedal Position Sensor 2-3 Correlation
P1273 Accelerator Pedal Position Sensor 1-3 Correlation
P1275 Boost Control Condition (except 1997-98 Corvette)
P1275 Accelerator Pedal Positioning (APP) Sensor 1 Circuit (1997-98 Corvette)
P1276 Accelerator Pedal Positioning (APP) Sensor 1 Circuit Performance
P1280 Accelerator Pedal Positioning (APP) Sensor 2 Circuit
P1281 Accelerator Pedal Positioning (APP) Sensor 2 Circuit Performance
P1285 Accelerator Pedal Positioning (APP) Sensor 2 Circuit
P1286 Accelerator Pedal Positioning (APP) Sensor 2 Circuit Performance
P1300 Ignition Coil 1 Primary Feedback Circuit
P1305 Ignition Coil 2 Primary Feedback Circuit
P1310 Ignition Coil 3 Primary Feedback Circuit
P1315 Ignition Coil 4 Primary Feedback Circuit
P1320 ICM 4X Reference Circuit Too Many Pulses (except 1996-98 4.0L)
P1320 ICM 4X Reference Circuit Intermittent No Pulses (1996-98 4.0L)
P1323 ICM 24X Reference Circuit Low Frequency
P1335 Crankshaft Positioning Sensing Circuit
P1336 CKP System Variation Not Learned
P1345 Camshaft To Crankshaft Position Correlation Fault
P1346 CKP Sensor System Variation Not Learned/ Intake Camshaft Position Performance
P1349 Intake Camshaft Position System
P1350 Ignition Control System
P1351 Ignition Control Circuit Voltage High (except 1998 3.1L)
P1351 Ignition Control Circuit Open (1998 3.1L)
P1352 Bypass Circuit Open Or Voltage High
P1359 Ignition Coil Group 1 Control Circuit
P1360 Ignition Coil group 2 Control Circuit
P1361 IC Circuit Not Toggling
P1361 Ignition Control Circuit Voltage Low (Distributor Ignition)
P1362 Bypass Circuit Shorted Or Voltage Low
P1370 ICM 4X Reference Too Many Pulses
P1371 ICM 4X Reference Too Few Pulses (except Caprice, Fleetwood, Impala SS & Roadmaster)
P1371 Distributor Ignition Low Resolution Circuit (Caprice, Fleetwood, Impala SS & Roadmaster)
P1372 CKP Sensor A-B Correlation
P1374 3X Reference Circuit
P1375 ICM 24X Reference Voltage Too High
P1376 Ignition Ground Circuit
P1377 ICM Cam Pulse To 4X Reference Pulse Comparison
P1380 ABS/EBCM/EB(T)CM DTC Detected/Rough Road Data Unusable
P1381 Misfire Detected No EBCM/EB(T)CM/PCM Serial Data
P1401 Exhaust Gas Recirculation (EGR) flow test fault
P1403 EGR Error
P1404 EGR Valve Closed Pintle Position
P1404 EGR Valve Stuck Open Or Circuit Performance
P1405 EGR Error
P1406 EGR Valve Pintle Position Circuit
P1408 MAP Sensor Circuit
P1410 Fuel Tank Pressure System
P1415 AIR System Bank 1
P1416 AIR System Bank 2
P1431 Fuel Level Sensor 2 Circuit Performance
P1432 Fuel Level Sensor 2 Circuit Voltage Low
P1433 Fuel Level Sensor 2 Circuit Voltage High
P1441 EVAP System Flow During Non-Purge
P1442 EVAP Vacuum Switch Circuit
P1450 BARO Sensor Circuit
P1451 BARO Sensor Circuit
P1460 Cooling Fan Circuit (except Catera)
P1460 Misfire Detected With Low Fuel (Catera)
P1483 Engine Cooling System Performance
P1500 Starter Signal Circuit
P1501 Theft Deterrent System
P1502 Theft Deterrent System No Password Received
P1503 Theft Deterrent System Password Improper
P1508 Idle Air Control (IAC) System Low RPM
P1509 IAC System High RPM
P1510 Back-Up Power Supply
P1511 Throttle Control System- Backup System Performance
P1514 TAC System MAF Performance
P1515 Command vs Actual Throttle Position Performance (PCM)
P1516 Command vs Actual Throttle Position Performance (TAC Module)
P1517 TAC Module Processor
P1518 PCM To TAC Module Serial Data Circuit
P1519 Throttle Actuator Control Module
P1520 Park/Neutral Position Switch Circuit, Gear Indicator System
P1523 Throttle Closed Position Performance
P1524 TPS Learned Closed Throttle Angle Degrees Out Of Range
P1526 TPS Learn Not Completed
P1527 Trans Range/Pressure Switch Comparison
P1530 Ignition Timing Adjustment Switch Circuit
P1530 A/C Refrigerant Pressure Sensor Error
P1531 Low Air Conditioning Refrigerant Charge
P1532 A/C Evaporator Temperature Circuit Voltage Low
P1533 A/C Low Side Temperature Sensor Circuit
P1535 A/C/ High Side Temperature Sensor Circuit
P1536 A/C System ECT Overtemperature
P1537 A/C Request Circuit Voltage Low
P1538 A/C Request Circuit Voltage High
P1539 A/C High Pressure Switch Circuit Voltage High
P1540 A/C System High Pressure
P1542 A/C System High Pressure/High Temperature
P1543 A/C System Performance
P1545 A/C Clutch Relay Control Circuit
P1546 A/C Clutch Relay Control Circuit Voltage Low (except 1996-98 Camaro/Firebird & 1997-98 Corvette)
P1546 A/C Clutch Status Circuit Voltage Low (1996-98 Camaro/ Firebird & 1997-98 Corvette)
P1550 Stepper Motor Speed Control
P1554 Speed Control Status Circuit
P1555 Electronic Variable Orifice Fault (Saturn)
P1558 Speed Control (SPS Low)
P1560 Speed Control System/Transaxle Not In Drive
P1561 Speed Control Vent Solenoid
P1562 Speed Control Vacuum Solenoid
P1564 Speed Control System/Vehicle Acceleration Too High (except Catera)
P1564 ECM Battery Voltage Loss (Catera)
P1565 Speed Control Servo Position Sensor
P1566 Speed Control System/Engine RPM Too High
P1567 Speed Control Switches/ABCS Active
P1568 Speed Control (SPS High)
P1570 Speed Control System/Traction Control Active
P1571 TCS Desired Torque Circuit (except 4.0L, 4.6L & 1997-98 5.7L Corvette)
P1571 Traction Control System PWM Circuit No Frequency (4.0L & 4.6L)
P1571 ASR Desired Torque (1997-98 5.7L Corvette)
P1572 Traction Control System Active Circuit Voltage Low Too Long
P1572 ASR/TCS Active Circuit Low Voltage Too Long
P1573 PCM/EBTCM Serial Data Circuit
P1573 Engine Hot Lamp Control Circuit
P1574 EBTCM System/Stop Lamp Circuit Voltage High (except 1997-98 Corvette)
P1574 Stop Lamp Control Circuit (1997-98 Corvette)
P1575 Extended Travel Brake Switch Circuit Voltage High
P1576 Brake Booster Vacuum Sensor Circuit Voltage High
P1577 Brake Booster Vacuum Sensor Circuit Voltage Low
P1578 Brake Booster Vacuum Sensor Circuit Low Vacuum
P1579 Park/Neutral To Drive/Reverse At High Throttle Angle
P1580 Cruise Control Module Move Circuit, Low Voltage
P1581 Cruise Control Module Move Circuit, High Voltage
P1582 Cruise Control Module Direction Circuit, Low Voltage
P1583 Cruise Control Module Direction Circuit, High Voltage
P1584 Cruise Control Disabled
P1585 Cruise Control Inhibit Output Circuit
P1586 Cruise Control Brake Switch 2 Circuit
P1599 Engine Stall Or Near Stall Detected
P1600 PCM Battery
P1600 Serial Communication Between PCM & TCM
P1601 Loss of Serial Communication (Except Catera)
P1601 ECM Overtemperature
P1602 Loss Of EBC/EBTCM Serial Data (Except Catera)
P1602 KS Module Circuit (Catera)
P1603 Loss Of SDM Serial Data
P1604 Loss of IPC Serial Data
P1605 Loss of HVAC Serial Data
P1607 Engine Oil Level Switch Circuit
P1610 Loss Of PZM Serial Data (1996-97 Except 1997 Cutlass & Malibu)
P1610 Failure With Body Function Controller (1997 Cutlass & Malibu)
P1610 Standard Body Module Series Data CKT (1998)
P1611 Loss Of CVRTD Serial Data
P1617 Engine Oil Level Switch Circuit
P1619 Engine Oil Lite Monitor Reset Circuit
P1620 Low Engine Coolant Level (Saturn)
P1621 PCM Memory Performance (Except 1998 5.7L)
P1621 VCM EEPROM Performance (1998 5.7L)
P1623 PCM Prom Error/ Transaxle Temperature Pull-Up Resistor Fault (Saturn Z body)
P1624 Customer Snapshot Data Available (Saturn)
P1625 TCM Flash Checksum Fault (Saturn)
P1626 Theft Deterrent System Fuel Enable Circuit
P1627 A/D Performance
P1628 PCM Engine Control Temp Pull-Up Resistor
P1629 Theft Deterrent System Fuel Enable Circuit Improper Signal Detected During Engine Cranking
P1629 Theft Deterrent Crank Signal Malfunction (1997-98 2.2L, 2.4L, 3.1L & 3.8L)
P1630 Theft Deterrent System/PCM/VCM in Learn Mode
P1631 Theft Deterrent System Password Improper
P1632 Theft Deterrent System Fuel Disabled
P1633 Ignition Supplemental Power Circuit Voltage Low
P1634 Ignition 1 Power Circuit Voltage Low
P1635 5 Volt Reference (A Or 1) Circuit
P1637 Alternator L Terminal Circuit
P1638 Alternator F Terminal Circuit
P1639 5 Volt Reference (B Or 2) Circuit
P1640 Driver 1 Input Voltage High
P1641 MIL Control Circuit (Except 5.7L VINs P & 5 & 1998 3.1L & 3.8L)
P1641 Fan Control Relay 1 Control Circuit (5.7L VINs P & 5)
P1641 A/C Relay Control Circuit (1998 3.1L & 3.8L)
P1642 Vehicle Speed Output Circuit (Except 3.4L, 5.7L VINs P & 5 & 1998 3.8L)
P1642 Fan Control Relay 2 & 3 Control Circuit (5.7L VINs P & 5)
P1642 AIR Control Circuit (3.4L)
P1642 Change Oil Lamp Control Circuit (1998 3.1L Lumina & Monte Carlo)
P1643 Fuel Pump PWM Control Circuit (Except 5.7L VINs P & 5)
P1643 Engine RPM Output Circuit (5.7L VINs P & 5)
P1644 Delivered Torque Output Circuit
P1645 Boost Control Solenoid Circuit (Except 4.0L & 4.6L)
P1645 EVAP Solenoid Output Circuit (4.0L & 4.6L)
P1646 Boost Control Solenoid Control Circuit (Except 4.0L & 4.6L)
P1646 EVAP Vent Valve Output Circuit (4.0L & 4.6L)
P1650 Driver 2 Input Voltage High
P1651 Fan On Relay Control Circuit/Output Driver Module (Quad Driver) 'B' Quickset Fault (Saturn)
P1651 Fan 1 Relay Control Circuit
P1652 Fan 2 Relay Control Circuit (Except Cadillac & Corvette)
P1652 VSS Output Circuit (1996 Corvette)
P1652 Powertrain Induced Chassis Pitch Output Circuit (1997- 98 Corvette)
P1652 Lift/Drive Output Circuit (Cadillac)
P1653 TCS Delivered Torque Control Circuit (Except Caprice, Roadmaster & 1998 3.8L)
P1653 Oil Level Lamp Control Circuit (Caprice, Fleetwood & Roadmaster)
P1653 Fuel Level Output Control Circuit (1998 3.8L)
P1654 A/C Relay Control Circuit (Except 4.0L & 4.6L)
P1654 Cruise Disable Output Circuit (4.0L & 4.6L)
P1655 EVAP Purge Solenoid Control Circuit
P1656 Wastegate Solenoid Control Circuit
P1657 Skip Shift 1-4 Upshift
P1660 Cooling Fan Control Circuits
P1661 MIL Control Circuit
P1662 Speed Control Inhibit Control Circuit
P1663 Alternator Lamp Control Circuit (Except Caprice, Fleetwood & Roadmaster)
P1663 Change Oil Lamp Control Circuit (Caprice, Fleetwood & Roadmaster)
P1664 Skip Shift 1-4 Upshift Lamp Control Circuit
P1665 DBCM/DBTCM Serial Data Circuit (1996-97)
P1665 EVAP Vent Valve Solenoid Control Circuit (1998)
P1667 Reverse Inhibitor Solenoid Control Circuit (1996-97)
P1667 Fuel Pump Speed Control Circuit (1998)
P1670 QDM 4 Circuit
P1671 MIL Control Circuit
P1671 Oil Change Lamp Control Circuit
P1672 Low Engine Oil Level Lamp Circuit
P1673 Engine Hot Lamp Control Circuit
P1674 Tachometer Control Circuit
P1675 EVAP Vent Solenoid Control Circuit
P1676 EVAP Canister Purge Solenoid Control CKT
P1689 TCS Delivered Torque Control Circuit
P1700 MIL Requested By TCM
P1701 MIL Request Circuit
P1740 Torque Management Request Circuits, Transmission & Traction Control (Except Catera)
P1740 Torque Control/Management Request Circuits (Catera)
P1760 Transmission Control Module Supply Voltage Interrupted
P1780 Park Neutral Position Switch Circuit
P1781 Engine Torque Signal Circuit
P1792 ECM To Transmission Control Module Engine Coolant Signal
P1800 ECM To Transmission Control Module Engine Coolant Signal
P1810 ATF Pressure Manual Valve Position Switch Malfunction
P1811 Long Shift & Max Adapt
P1812 TOT Condition
P1814 Torque Converter Overstress
P1819 Internal Mode Switch - No Start
P1820 Internal Mode Switch Circuit 'A' Low
P1822 Internal Mode Switch Circuit 'B' Low
P1823 Internal Mode Switch Circuit 'P' Low
P1825 Internal Mode Switch - Invalid Range
P1826 Internal Mode Switch - Invalid Range
P1835 Kickdown Switch Circuit
P1842 1-2 Shift Solenoid Circuit Low Input
P1843 1-2 Shift Solenoid Circuit High Input
P1845 2-3 Shift Solenoid Circuit Low Input
P1847 2-3 Shift Solenoid Circuit High Input
P1850 Brake Band Apply Solenoid
P1860 TCC PWM Solenoid Circuit
P1864 TCCEnable Solenoid Circuit
P1868 Transmission Fluid Life
P1870 Trans Component Slipping
P1873 Torque CONV Stator Temp Switch Circuit Low
P1874 Torque CONV Stator Temp Switch Circuit High
P1875 4WD Low Switch Circuit Electrical
P1886 Transaxle Shift, Timing Solenoid Performance
P1887 TCCRelease Switch Malfunction
P1890 Throttle Position Signal Input
P1895 Engine Torque Delivered Circuit
especially on the more modern cars that are computer controlled, the days of effectively tuning by ear and vacuum gauge and engine sound went out with carbs
you need a few basic tools, now the list will vary, but you can,t get by by guessing, you neet to know and test now that sensors and CPUs control engine function
heres some basic tools
be sure to get the specific manuals your car and EFI system and ignition system,require FIRST
while it appears to be expensive, it saves you a good deal of money in the long run compared to dealing with the local chevy dealers mechanics, and makes diagnostics far faster, I bought this for the shop and it seems to be a good investment, since between a dealers diagnostics and swapping parts that don,t need changing you could easily spend close to that on just a few problems getting sorted out
youll also want a few basic diagnostic tools
and a book or two
in no time youll be the area wizz kid on chevy injection diagnostics
This is from http://shbox.com/
A fuel pressure test gauge can be bought at your local auto supply for ~$35. Attach it to the schrader valve that is on the fuel rail. Schrader valve location on 1994-1997
Normal pressure when the engine is not running and lines have been pressurized is 41-47 psi. This same pressure should be observed at wide open throttle (WOT). WOT can be simulated by removing the vacuum hose to the regulator at idle. At idle (because of the effect of the vacuum to the regulator) pressure will be less than what you observe with the vacuum line off. There may be anything from a 3 to 10 psi difference. NOTE: any indication of fuel in the vacuum line to the regulator, means the regulator is leaking and should be replaced. Check the line for fuel or the smell of fuel.
To fully determine that you don't have a pressure drop off during actual WOT situations, you should tape the gauge to your windshield and take it for a test run. This will tell you if the pump can meet actual fuel flow demands at pressure and not just at a simulated WOT condition (as when removing the vacuum to the regulator).
When you have a gauge connected and the pressure looks initially good and then bleeds off quickly when you shut the engine off, you can do a couple of tests to help you figure out where the pressure loss is.
What the factory manual says to temporarily install, is a set of "fuel line shut off adapters" (probably something the normal guy is not going to have available). You remove the fuel lines from the rail and connect these valves in between. This lets you shut off either side of the lines for testing.
You can do the same thing by pinching the flexible lines to shut them off, but risk breaking them. You might be able to do it (your risk) by using a needle nose vise grips and putting some scrap hose as cushions on the jaws. Then use that to clamp off the line just enough to seal it. Obviously, this is not the best way to shut off the lines and could result in breakage. Heat and age can make the hoses brittle. If you don't want to risk it, don't. It's just a suggestion.
You can use the fuel pump prime connector for pressurizing the system (jumper 12v to it to run the pump).
Watch your gauge as you jumper the prime connector. When you have good pressure remove the jumper and clamp off (or use shut off valve) the fuel supply line (3/8 pipe). If pressure holds, you have a leak on the feed line somewhere before it gets to the clamp (or shut off valve) or at the check ball in the pump. If it still goes down, release your clamp (or open shut off valve). Pressurize the system again, then remove the jumper and this time clamp (or shut off) the return line (5/16 line). If pressure holds, then the regulator is faulty. If pressure does not hold, you need to locate leaky injector(s). If you can't tell a leaky injector from reading the plugs, you can look and see if injectors are leaking by removing the fuel rail screws and pull the rail and all the injectors up, so you can see under them. Leave them over the injector ports. Pressurized the system and look under the injectors to see if any are dripping.
(I) test the injectors first, remove the regulator and plug the fuel rail, if the fuel pressure dropping off problem stops with the fpr removed its a defective pressure regulator if it continues its very likely a defective injector(S) if they (injector(S) minus the FPR) hold steady pressure testing the FUEL PRESSURE regulator next, is pointless ,its defective, if the fuel pressure dropping off problem starts again once its reinstalled its a defective pressure regulator
YEAH! I KNOW HOW DO YOU PLUG THE FUEL RAIL
HOME DEPOT sells rubber corks, and you hold them temporarily in place for testing with a vise grip
if its defective replace it with an adjustable version
IVE generally found no problem with any corvette LT1 or TPI efi if it will quickly build a minimum of 38-40PSI on start up and MAINTAIN at LEAST 38-40 psi for a MINIMUM of 10 minutes after the engines turned off, 40-42 lbs is what the factory tests want and expect so if your getting 38-40psi your pressure readings indicate a normal, perhaps even better than average pressure reading, and more than expected pressure retention,
IF you suspect a TPI has a defective injector that's leaking or not flowing fuel,or partly clogged...You can also test this, to a degree, with a fuel pressure gauge
you can install a fuel pressure gauge on the fuel rail, and turn on the ignition key then watch the gauge, it should jump to 37-42 psi then remain fairly steady for at least 5 minutes before gradually loosing pressure.
If you can - and this is a pain in the butt to do, temporarily- remove the injectors. Leave them on the rail, but remove the rail. from the intake itself, This requires removing the majority of the TPI (P.I.T.A. but required).
yeah. a good quality and properly adjusted, adjustable fuel pressure regulator is generally going to potentially provide,
just enough more consistent fuel delivery volume to be worth a few extra hp, but its major benefit is in the fact in many cases,
it can easily result in 30- plus hp over a improperly functioning O.E.M, fp regulator. (not all that rare)
keep in mind theres a huge difference between replacing a fully functional O.E.M. fuel pressure regulator ,
with an aftermarket adjustable regulator ,
which may or may not provide any benefits and replacing,
a mal functional, O.E.M. fuel pressure regulator with an aftermarket adjustable regulator ,
Dyno Comparisons -- Adjustable Fuel Pressure Regulator Settings
Here, the dyno shows a 16.6 horsepower
and 14.6 ft/lbs torque
difference between the stock fuel pressure (46psi) and 36psi with the LG Motorsports adjustable regulator. Actually, it was still making more power at 35psi than 36psi, but until I can measure my O2 sensors, I did not want to lean it out any further. The average gain here was 13.9 horsepower
and 15.4 ft/lbs torque
. Check out the Dynojet Race Routine
between the stock and 36psi fuel pressure.
Something new: Dynojet is currently Beta testing their new WinPEP software for the dyno. With this software, they have the ability to graph up to 12 graphs at once. Check out the Dynojet WinPEP Graph
of all the power between the stock and 35psi fuel pressures.
One thing that I have found after some time with this mod is that the stock computer is quite smart. After lowering fuel pressure to achieve a better air/fuel ratio, the computer sees this at part throttle and adds injector pulsewidth to compensate. Basically, horsepower fell back off to where I started from. While normal trains of thought tell us that since O2 values are not measured during wide open throttle, that fuel pressure should have a long lasting effect here. Actually, it does not. The computer uses the last known long term fuel trim integer at WOT, which is to add fuel since at part throttle it has adjusted for being too lean.
Remove the rail, but leave it connected to the fuel lines.
Next up, put a strip of cardboard under each bank. Then, have a buddy turn the ignition key on but not try to start the engine , you should hear the fuel pump run for 3 seconds while you look to see what happens. You should get an immediate spray of fuel.(all should be about equal and no injector remains dripping fuel) now have your buddy Turn off the key, while you watch closely to see which injectors are leaking.
Intake Air Temp sensor. It is located on the bottom of the inlet plenum a few inches ahead of the distributor. It is like right next to the fuel pressure regulator., it can effect fuel flow rates
basic fuel injector test
now Ill assume your battery reads over 12 volts and the starter works, and easily spins the engine
the first step
find the fuel rail shrader valve and remove the cap and connect the fuel pressure gauge
if you turn on the ignition key to get the dash and accessories to light up but don,t start the engine,the fuel pump,
should briefly run to pressurize the fuel rail to about 38psi-42 psi,
this should stay at this pressure level for at least 5 minutes minimum, if it drops slowly your fuel rail is leaking fuel.
now the fuel pressure regulator may be defective or leaking, or in very rare cases the fuel pump may be defective ,
but the most likely cause is a fuel injector(s) stuck in the open position.
next pull the injector harness,
off a single injector at a time, press the wire bar to release the clip, retention, then pull it up and off, the noid light plugs into the harness,
use the spare injector pig tail
on the now disconnected injector ,connect the multi meter on ohms setting and it should read 11-13 ohms injector on each injector tested.
if it reads under 9 ohms or over 20 ohms its a defective injector
now use a couple 3 ft long test leads connect one too one of the pig tail test leads
and to 12 volts, connect the other pig tail lead too a different test lead and watch the fuel pressure gauge,with the key out of the ignition , you should have 38-42 psi of fuel rail pressure, watch carefully while you tap the second test lead to ground (the plenum or alternator case works) the fuel pressure should drop as you tap the ground pig tail lead, this verifies the injector function at least partially, if you don,t see the pressure drop the injectors not allowing fuel flow through it and should be replaced.
after you complete each injector test , turn the ignition key on, to re-pressurize the fuel trail and reconnect the harness to the previously tested injector,
repeat the noid light and pig-tail function fuel pressure test on each of the other injectors individually.
youll need a fuel pressure gauge and multi meter
it helps if you have a spare fuel injector pig-tail for testing
having a NOID light injector harness tester wont hurt either
on the TPI and LT1 efi and many other EFI intakes,
theres a shrader valve,
that can be easily accessed to check fuel rail pressure,
dealing in facts you verify is always preferable.
GM part number for the complete fuel rail o-ring kit is 17111696
if your TPI FUEL PRESSURE REGULATOR DIAPHRAGM LEAKS youll find it difficult or impossible to be starting your car
heres a link to the correct o-rings they are light blue
NAPA sells them at times
all the o-rings on the fuel rails and injectors need to be dipped in thin oil so they insert and slide into place with less friction, this tends to greatly reduce the chance of the o-rings ripping, and yes you need the correct o-rings that fit correctly to begin with if you expect the rings to seal correctly
17113544 - Injector Seals
17111696 - O-Ring Kit
22514722 - Fuel Inlet O-Ring
22516256 - Fuel Inlet O-Ring