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
- Verify the on-car diagnostics are working by performing ON -BOARD DIAGNOSTIC (OBD) SYSTEM CHECK chart in BASIC TESTING article in the ENGINE PERFORMANCE section.
- Ensure the PCM and Malfunction Indicator Light (MIL) are functioning properly.
- Ensure there are no diagnostic trouble codes stored, or only intermittent codes are present.
- Ensure the fuel control system is operating properly. See BASIC TESTING article in the ENGINE PERFORMANCE section.
- Perform fuel system pressure test in BASIC TESTING article in the ENGINE PERFORMANCE section.
- 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, ignition control, TCC, etc. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section for test procedures.
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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.