Knock Sensor Circuit
- An open or short circuit on ESC wire to PCM will cause a loss of 12-volt ESC controller signal. This will cause PCM to fully retard ignition timing.
- If a scan tool 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 tool.
- If a scan tool is not available, backprobe PCM 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 PCM terminal should drop to zero volts, and return when knock signal ceases.
- 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 appropriate KNOCK SENSOR (KS) CIRCUIT DTC under TESTS W/CODES article.