DTC 43

Electronic Spark Control Circuit:

Circuit Description:
The knock sensor is used to detect engine detonation and allow the PCM to retard the Electronic Spark Timing (EST) based on the signal being received. The circuitry within the knock sensor causes the PCM's supplied 5 volts signal to be pulled down, so that under a no knock condition CKT 496 would measure about 2.5 volts. The knock sensor produces an AC signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency is dependent upon the knock level.

If CKT 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.

Code 43 will set if:

^ Voltage on CKT 496 goes above 3.4 volts or below 1.5 volts.

^ Either condition present for 20 seconds.

Code 43 Diagnostic Chart:

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. If a Code 43 is detected, the PCM 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. The PCM applies a 5 volts through a pull-up resistor which should be present at the knock sensor terminal.

3. This test determines if the knock sensor is faulty or if the ESC portion of the MEM-CAL is faulty.

Diagnostic Aids:
Check CKT 496 for a intermittent open or short to ground. Also check for proper installation of MEMCAL.

If the ESC CKT 496 is routed too close to secondary ignition wires it may induce a voltage and cause a false knock signal.

^ Detonation/Spark Knock/Pings