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 MANUALSCHEVROLET1987HI-CUBE 6.2 J, 475/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 21 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - GASOLINE)IGNITION SYSTEMTIMING CONTROL SYSTEMS (C-4 & C-5)C-5, KNOCK SENSOR CIRCUIT (MODELS USING EXTERNAL SPARK CONTROLLER MODULE)
1987 Chevrolet Hi-Cube 6.2 J, 475/M40
C-5, Knock Sensor Circuit (Models Using External Spark Controller Module)
1987 Chevrolet Hi-Cube 6.2 J, 475/M40SECTION C-5, 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 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Rally Camper Special, 1994 GMC Rally, and 1994 GMC Forward Control. However, it is still accessible from the selected car via links, so may be relevant.
- An open or short circuit on ESC wire to ECM will cause a loss of 12-volt ESC controller signal. This will cause ECM to fully retard ignition timing.
- If a scan tester 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 tester.
- If a scan tester is not available, backprobe ECM 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 ECM terminal should drop to zero volts, and return when knock signal ceases.
- If signal does not respond as described, check knock sensor signal to controller 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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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.