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 MANUALSPONTIAC1987FIREBIRD FORMULA, 5.0 H, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM1987-88 COMPUTERIZED ENGINE CONTROLSCHART C1B - CRANK SIGNAL
1987 Pontiac Firebird Formula, 5.0 H, Automatic
Chart C1B - Crank Signal
1987 Pontiac Firebird Formula, 5.0 H, AutomaticSECTION Chart C1B - Crank Signal
Crank signal is a 12-volt signal to ECM during cranking to allow enrichment and cancel diagnostics until engine is running or 12 volt is no longer on circuit.
- Checks for normal (cranking) voltage to terminal C9 of ECM. Test light should be on during cranking.
- Determines if source of blown fuse was a faulty ECM.
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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.