DTC 43

Code Chart 43:

Knock Sensor Circuit:

CIRCUIT DESCRIPTION:
The knock sensor is used to detect engine detonation and allow the ECM to retard the Ignition Control (IC) timing based on the signal being received. The circuitry within the knock sensor causes the ECM's supplied 5.0 volt signal to be pulled down, so that under a no knock condition CKT 496 should 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 20.0 seconds, DTC 43 will be stored.

DTC 43 will set if:

^ Ignition "ON."
^ Voltage on circuit 496 goes above 3.5 volts or below 1.5 volts.
^ Condition present for 20.0 seconds.

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

1. If DTC 43 is detected, "Knock Retard" on the scan tool will display 10.0 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 ECM applies 5.0 volts to CKT 496, which should be present at the knock senor terminal.

3. This test determines if the knock sensor is faulty or if the knock sensor portion of the PROM is faulty.

DIAGNOSTIC AIDS:
Check CKT 496 for an intermittent open or short to ground. Also check for proper installation of PROM. If knock sensor circuit 496 is routed too close to secondary ignition wires, it may induce a voltage and cause a false knock signal. - Intermittent Malfunctions