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.
Preliminary Checks
This portion of article is used only AFTER you have checked the following:
- Verify the on-car diagnostics are working by performing DIAGNOSTIC CIRCUIT CHECK located in BASIC TESTING article in this section.
- Verify that the ECM and "SERVICE ENGINE SOON" light are functioning properly.
- Verify that there are no trouble codes stored, or only intermittent ones.
- Verify that the fuel control system is operating properly by performing appropriate SYSTEM PERFORMANCE CHECK chart (carbureted models), FIELD SERVICE MODE CHECK (fuel injected models except Cadillac) or PFI SYSTEM CHECK (Cadillac except Brougham) located in BASIC TESTING article in this section.
- Perform fuel system pressure test on EFI vehicles.
- Perform a careful visual inspection of all systems.
After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally recommend testing of a system or component on vehicle, such as EGR, EST, TCC, etc. These are covered in the SYSTEM/COMPONENT TESTS article in this section.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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