Chart C-5 Knock Sensor (KS) System Check

Chart C-5 Knock Sensor System Check:

Knock Sensor Wiring Circuit:

CIRCUIT DESCRIPTION:
Spark retard is accomplished with the knock sensor module that sends a signal to the PCM when detonation is detected. As the knock sensor detects engine knock, the voltage from the KS module to the PCM is reduced. This signals the PCM to retard timing, when engine speed is above approximately 1500 RPM or vehicle speed is greater than 10 mph.

CHART TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If a DTC 43 is not set, but a knock signal is indicated while running above 1500 RPM, listen for an internal engine noise. Under a no load condition, there should not be any detonation, and if knock is indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by tapping on the right exhaust manifold. This test can also be performed at idle. Test number 1 was run above 1500 RPM, to determine if a constant knock signal was present, which would affect engine performance.
3. This tests whether the knock signal is due to the sensor, a basic engine problem, or the KS module.
4. If the module ground circuit is faulty, the KS module will not function correctly. The test light should light indicating the ground circuit is OK.
5. Contacting CKT 496 with a test light to 12 volts, should generate a knock signal. This determines whether the knock sensor is faulty or the KS module can't recognize a knock signal.

DIAGNOSTIC AIDS:
If the KS system checks OK, but detonation is the complaint, refer to "Detonation/Spark Knock" in "Diagnosis By Symptom." Detonation/Spark Knock/Pings