Knock Sensor Circuit

1996 Isuzu Trooper S, AutomaticSECTION Knock Sensor Circuit
  1. 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.
  2. 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.
  3. 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.
  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 appropriate KNOCK SENSOR (KS) CIRCUIT DTC under TESTS W/CODES article.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
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