Knock Sensor: Testing and Inspection

CHART C-5
KNOCK SENSOR (KS) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE, OR POOR ECONOMY)

Circuit Description:
KS is accomplished with a module that sends a voltage signal to the Engine Control Module (ECM). As the KS detects engine knock, the voltage from the KS module to the ECM is shut "OFF" and this signals the ECM to retard timing, if engine rpm is over about 900.

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1. If a Diagnostic Trouble Code 43 is not set, but a knock signal is indicated while running at 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 at 1500 rpm, to determine if a constant knock signal was present, which would affect engine performance.
3. This tests whether the Knock Sensor (KS) 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 terminal "E" of KS module harness with a test light to 12 volts, should generate a knock signal to determine whether the KS is faulty, or the KS module can't recognize a KS signal.

Diagnostic Aids:
If the KS system checks OK, but detonation is the complaint, refer to "Detonation/Spark Knock" symptom in "Symptoms".




CHART C-5
KNOCK SENSOR (KS) SYSTEM CHECK
(ENGINE KNOCK, POOR PERFORMANCE1 OR POOR ECONOMY)
THIS CHART SHOULD BE USED AFTER ALL OTHER CAUSES OF SPARK KNOCK HAVE BEEN CHECKED. I.E., TIMING, EXHAUST GAS RECIRCULATION, ENGINE TEMPERATURE OR EXCESSIVE ENGINE NOISE, ETC. IF DIAGNOSTIC TROUBLE CODE (DTC) 43 15 SET, USE THAT CHART FIRST.
"AFTER REPAIRS," REFER TO DTC CRITERIA AND CONFIRM DTC DOES NOT RESET.