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 23 (ENGINE CONTROLS - TESTS W/CODES - 6.5L DIESEL)DIAGNOSTIC TROUBLE CODE CHARTSCHART A-1 - NO MIL (SERVICE ENGINE SOON LIGHT)NOTES
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40
Chart A-1 - No Mil (Service Engine Soon Light): Notes
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40SECTION Notes
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
MIL should be on when engine is off and ignition is on. Switched battery voltage is supplied to MIL. The PCM turns light on by providing a ground path through the MIL (SERVICE ENGINE SOON) control circuit.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- If fusible link is blown, see WIRING DIAGRAMS at the end of this article for complete circuit.
- Using a test light connected to 12 volts, probe each of the system ground circuits to ensure a good ground is present. See PIN VOLTAGE CHARTS article in this section.
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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.