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 MANUALSCHEVROLET1985FORWARD CONTROL 6.2 J, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISDIESEL CEC TESTS W/CODESBASIC DIAGNOSTIC PROCEDURE
1985 Chevrolet Forward Control 6.2 J, Standard
Basic Diagnostic Procedure
1985 Chevrolet Forward Control 6.2 J, StandardSECTION Basic Diagnostic Procedure
Any diagnosis of the DEC system should be performed in the following order:
- Ensure that all engine systems not related to the DEC system are operating properly. This should include a careful visual underhood inspection including: all vacuum hoses for correct routing, pinches, cuts, or disconnects; all wires in engine compartment for correct and good connections, burned or chaffed spots, pinched wires, or contact with sharp edges or hot exhaust manifolds.
- Perform Diagnostic Circuit Check and continue diagnosis as indicated in chart. This check will either verify proper DEC system and ECM operation, or direct you to a specific trouble code chart(s) or another DEC system chart.
- If any trouble codes are stored, start with the lowest numbered code and diagnose using the appropriate trouble code chart. If code 51, 52 or 53 are stored, always go to that chart FIRST.
- After any repair to the DEC system, the Diagnostic Circuit Check must be repeated to verify proper system operation.
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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.