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Home >> GMC >> 1998 >> Suburban K2500, 6.5 F >> Repair and Diagnosis >> External Pages >> Different car >> Section 32 (Engine Controls - System & Component Testing - 6.5L) >> Ignition System >> Timing Control Systems >> Knock Sensor Circuit (Models Using External Spark Controller Module)

Knock Sensor Circuit (Models Using External Spark Controller Module)

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1997 GMC Yukon, 1997 GMC Suburban, 1997 GMC Pickup, 1997 GMC Cab & Chassis, and 1997 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. An open or short circuit on IC module control wire to PCM will cause a loss of 12-volt IC module 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 to original voltage when knock signal ceases.
  4. If voltage signal does not respond as described, check knock sensor-to-module-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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