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C-5, Knock Sensor Circuit (Models Using External Spark Controller Module)

WARNING: This page is about a different car, the 1995 GMC Sonoma and 1995 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. An open or short circuit on ESC wire to ECM/PCM/VCM will cause a loss of 12-volt ESC controller signal. This will cause ECM/PCM/VCM to fully retard ignition timing.
  2. If a scan tester is available, connect tester to Data Link Connector (DLC). Using a metal object, tap on engine next to knock sensor and note knock parameter. Knock should be indicated on scan tester.
  3. If a scan tester is not available, backprobe ECM/PCM/VCM knock sensor signal terminal with a DVOM. With engine idling, 8-12 volts should be present at this terminal. Using a metal object, tap on engine close to knock sensor. Voltage signal at ECM/PCM/VCM terminal should drop to zero volts, and return when knock signal ceases.
  4. If signal does not respond as described, check knock sensor-to-controller-signal. On vehicles equipped with automatic transmission, it may be necessary to place transmission in Drive for timing change to occur. See KNOCK SENSOR  under ENGINE SENSORS & SWITCHES.
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