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 MANUALSCHEVROLET1987STEP VAN P20, 7.4 W, AUTOMATIC, 400/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 12 (ENGINE CONTROLS - TESTS W/CODES - 4.3L)SELF-DIAGNOSTIC SYSTEMHARD OR INTERMITTENT TROUBLE CODE DETERMINATION
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40
Hard Or Intermittent Trouble Code Determination
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40SECTION Hard Or Intermittent Trouble Code Determination
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 1994 Oldsmobile Bravada, 1994 GMC Vandura, 1994 GMC Sonoma, 1994 GMC Safari, and 1994 GMC Rally. However, it is still accessible from the selected car via links, so may be relevant.
During any diagnostic procedure, determine if codes are due to hard or intermittent failure. Diagnostic charts will not usually help diagnose intermittent codes. To determine hard codes and intermittent codes, proceed as follows:
- MANUALLY enter diagnostic mode. Read and record all stored trouble codes. Exit diagnostic mode and clear trouble codes. See CLEARING TROUBLE CODES .
- Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL should go out. Run warm engine at specified curb idle for 2 minutes and note MIL.
- If MIL comes on, manually enter diagnostic mode. Read and record trouble codes. This reveals hard failure codes. Codes 13, 15, 24, 44, 45 and 55 may require a road test to reset hard failure after trouble codes were cleared.
- If MIL does not come on, all stored trouble codes were intermittent failures. Exceptions are noted under DIAGNOSTIC PROCEDURE.
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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.