Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1995FORWARD CONTROL 4.3 Z, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)EXTERNAL PAGESDIFFERENT CARSECTION 115 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 5.0L)IGNITION SYSTEMTIMING CONTROL SYSTEMS (C-4 & C-5)C-5, KNOCK SENSOR CIRCUIT (MODELS USING KNOCK SENSOR WITH INTERNAL SPARK CONTROLLER MODULE)
1995 GMC Forward Control 4.3 Z, Standard
C-5, Knock Sensor Circuit (Models Using Knock Sensor With Internal Spark Controller Module)
1995 GMC Forward Control 4.3 Z, StandardSECTION 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 8 other vehicles, including the 1995 GMC Vandura, 1995 GMC Rally, 1995 GMC Pickup, 1995 Chevrolet Sportvan, and 1995 Chevrolet Pickup. However, it is still accessible from the selected car via links, so may be relevant.
- 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.
- 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.
- 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.
- 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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When to See a Mechanic
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.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.