LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 1999 >> Jimmy 4D Utility, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Component Tests >> Ignition System >> Timing Control Systems >> Knock Sensor Circuit (Models Using Knock Sensor With Internal Spark Controller Module)
September 30: LEMON manuals is back up on a temporary server! Slowness is possible

Knock Sensor Circuit (Models Using Knock Sensor With Internal Spark Controller Module)

  1. An open or short circuit on knock sensor wire to PCM/VCM will set a related DTC. A false detonation signal will not cause PCM/VCM to set a DTC.
  2. Install scan tool. 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, 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-PCM/VCM circuit.
  4. On vehicles equipped with automatic transmission, it may be necessary to place transmission in Drive for timing change to occur.