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 MANUALSGMC1989MAGNAVAN 5.7 K, 3L80/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMCCC TBI TESTS W/CODESDIAGNOSTIC CHARTSCHART A4 - INJECTOR CIRCUIT DIAGNOSIS (ALL EXCEPT 2.5L)CIRCUIT DESCRIPTION
1989 GMC Magnavan 5.7 K, 3L80/M40
Circuit Description
1989 GMC Magnavan 5.7 K, 3L80/M40SECTION Circuit Description
Use this chart ONLY if CHART A3 indicated an injector circuit problem. If both injector circuits fail to blink when tested, diagnose one injector circuit at a time.
RENDER: 1.0x
NO RELATED
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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.