Code 43: Electronic Spark Control (ESC): Notes

The ECM supples a 5-volt reference on the knock sensor signal line. Internal sensor circuitry will cause this voltage to pull down to about 2.5 volts PC. The knock sensor produces an AC voltage signal when knock occurs. This AC voltage signal will ride on the PC signal back to the ECM. Code 43 will set if voltage on circuit No. 496 is greater than 3.5 volts or less than 1.5 volts and this condition is met for 20 seconds.

1. If a Code 43 is detected, the ECM will retard spark timing by 10 degrees. If an audible knock is heard from the engine, repair the internal engine problem. Normally, no knock should be heard at idle.
2. If taping on the engine lift hook does not produce a knock signal, try tapping on the engine closer to the sensor before proceeding.
3. The ECM has a 5-volt pull up resistor which places a 5-volt reference on the knock sensor signal line.
4. This test determines if the knock sensor is faulty or if the ESC portion of the MEMCAL is faulty.