Powertrain Controls - ECM/PCM

Code 43 Chart:

Code 43 Wiring Diagram:

CIRCUIT DESCRIPTION
The knock sensor is used to detect engine detonation and the Electronic Control Module (ECM) will retard the electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the ECM's supplied 5 volt signal to be pulled down, so that under a no knock condition circuit 496 would measure about 2.5 volts. The knock sensor produces an A/C signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency is dependent upon the knock level. If circuit 496 becomes open or shorted to ground, the voltage will either go above 3.5 volts or below 1.5 volts. If either of these conditions are met for 20 seconds, a Code 43 will be stored.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. Code 43 will set if:
^ Voltage on circuit 496 goes above 3.5 volts or below 1.5 volts.
^ All conditions present for 20 seconds.

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 detected at idle.

2. If tapping on the engine lift hook does not produce a knock signal, try tapping engine closer to sensor before proceeding.

3. The ECM has a 5 volt pull-up resistor which should be present at the knock senor terminal.

4. This test determines if the knock sensor is faulty or if the Electronic Spark Control (ESC) portion of the Mem-Cal is faulty.

DIAGNOSTIC AIDS
Check circuit 496 for a potential open or short to ground. Also check for proper installation of Mem-Cal. Refer to Diagnosis By Symptom / Intermittents.