DTC 43

Code 43:

ESC Wiring Diagram:

CODE 43

ELECTRONIC SPARK CONTROL (ESC) CIRCUIT


Circuit Description:

The ESC system is comprised of a detonation sensor and an ESC module.
As long as the ESC module is sending a voltage signal (8 to 10) volts to the ECM (no detonation detected by the ESC sensor), the calculated spark advance (EST) remains unaffected by the ESC input.
When the sensor detects detonation, the module turns "OFF" the circuit to the ECM and the voltage at ECM terminal "L" drops to 0 volt. The ECM then retards EST as much as 20 degrees in one (1) degree increments to reduce detonation. This happens fast and frequently enough that if looking at this signal with a DVM, you won't see 0 volt, but an average voltage somewhat less than what is normal with no detonation.
A loss of the detonation sensor signal or a loss of ground at ESC module would cause the signal at the ECM to remain high. This condition would result in the ECM controlling EST as if no detonation were occurring and could result in pre-ignition and potential engine damage.
Loss of the ESC signal to the ECM would cause the ECM to constantly retard the EST to its max retard or 20 degrees from the initial spark timing. This could result in sluggish performance and cause a Code 43 to set.
Code 43 will set when the engine is running and ESC input signal has been low more than 3.9 seconds.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. If the knock retard is reading high, the ECM is monitoring a low voltage signal on CKT 457 at ECM terminal "L".

2. Probing ESC harness terminal "C" with a test light connected to 12 volts should result in the knock retard display reading low due to over 8 volts having been applied to ECM terminal through CKT 457.

3. If over 6 volts is measured at ECM terminal "L", CKT 457 is OK and the fault is due to a poor connection at the ECM or the ECM is faulty.


Diagnostic Aids:

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check for :

Poor Connection or Damaged Harness - Inspect ECM harness connectors for backed out terminal "L", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

Intermittent Test - If connections and harness check out OK "Scan" knock retard while moving related connectors and wiring harness. If the failure is induced, the knock retard will read "LOW" to "HIGH." This will help to isolate the location of the malfunction.