Can't resolve ("ESC") code "43" on a 1985 c4 corvette .

G E HUEY

Member
The (ESC) Electronic Spark Cntrl module & Knock sensor replaced & torqued to specs. Still producing CODE 43. HELP
 
CODE 43 - Electronic Spark Control Fault

Trouble Code 43 indicates that there may be a malfunction in the Electronic Spark Control (ESC) circuit.

ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. A knock sensor (located at the rear of the engine block) sends signals to an ESC module which then signals the ECM that knocking is being detected. The ECM will retard the timing by as much as 20 degrees in 1 degree increments. A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and may possibly result in engine damage, if there is detonation.

Loss of the ESC signal to the ECM will cause the ECM to constantly retard the timing to its maximum. This results in sluggish performance and a Code 43.


step one , if you have a timing light and a decent code scanner , delete trouble codes,
check your ignition timing and set it to about 6 degrees advanced at idle (near 770 rpm)
if after you drive the car for 15-30 minutes your code still remains its likely your knock sensors defective


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Last edited:
some reading on the threads posted below, a bit of logic and deductive reasoning, and a multi meter and a shop manual will go a long way toward finding and fixing the problem.

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor


Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

sensor locations

  • Mass Air Flow (MAF), mounts in intake ducting between air filter and throttle body.
  • Throttle Position Sensor (TPS), mounts on right side of throttle body.
  • Idle Air Control valve (IAC), mounts in small manifold on bottom of throttle body.
  • MAF power relay, in relay center on firewall beside master cylinder.
  • MAF burn off relay, in relay center on firewall beside master cylinder.
  • Manifold Air Temperature sensor (MAT), mounts in bottom of plenum near the back
  • Coolant Temperature Sensor (CTS), mounts on front right of intake manifold base, below IAC valve
  • Cold start switch, front right of intake manifold base, below CTS
  • Exhaust Gas Recirculation valve(EGR), on top of intake manifold base, centered under plenum
  • EGR solenoid, on top of intake manifold, rear, between distributor and valve cover.
  • EGR diagnostic switch, on base of EGR valve.
  • Electronic Spark Control (ESC)knock sensor, bottom right of engine block, in front of starter just above oil pan rail, in the coolant drain boss.
  • ESC module, in relay center on firewall beside master cylinder
  • Electronic Spark Timing (EST) module, on distributor.
  • Oxygen (O2) sensor, in left exhaust manifold.
  • Air Injection Reactor (AIR) convertor divert solenoid and port solenoid, both together at front of right valve cover.
  • Oil pressure switch, on Y fitting with oil pressure gauge sender mounted in the oil pressure boss on the top left rear of the engine block behind intake manifold base. (applies power to fuel pump if fuel pump relay or relay circuit fails).
  • Fuel pump relay, in relay center on firewall beside master cylinder.
  • Fuel vaper canister (charcoal can) solenoid, on top of charcoal can in front left corner of engine bay.
  • Air Conditioner (AC) pressure switch, in boss on AC high pressure side aluminum tube beside right strut tower.
  • vehicle speed sensor, back of speedometer.
  • Cooling fan relay, on core support beside battery.
Sensor Locations
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