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Home >> GMC >> 1996 >> Forward Control 4.3 W >> Repair and Diagnosis >> External Pages >> Different car >> Section 134 (Engine Controls - System/Component Tests - 7.4L) >> Ignition System >> Timing Control Systems (C-4 & C-5) >> C-5, Knock Sensor Circuit (Models Using Knock Sensor With Internal Spark Controller Module)
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C-5, Knock Sensor Circuit (Models Using Knock Sensor With Internal Spark Controller Module)

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 1995 GMC Vandura Special, 1995 GMC Vandura, 1995 GMC Suburban, 1995 GMC Rally Camper Special, and 1995 GMC Rally. However, it is still accessible from the selected car via links, so may be relevant.
  1. An open or short circuit on knock sensor wire to ECM/PCM/VCM will set a related trouble code. A false detonation signal will not cause ECM/PCM/VCM to set a code.
  2. If a scan tester is available, connect it to Data Link Connector (DLC). 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, connect tachometer to engine. Start engine and hold RPM above idle. Using a metal object, tap on engine close to knock sensor. A noticeable decrease in engine RPM should occur. If no RPM decrease occurred, check knock sensor to ECM/PCM/VCM circuit.
  4. 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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