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.
Diagnostic Procedure
Diagnosis of computerized engine control system should be performed in the following order:
- Perform visual inspection. Most driveability problems in the engine control system result from faulty wiring, poor electrical connections or leaking air and vacuum hose connections. To avoid unnecessary component testing, perform a visual inspection before beginning DIAGNOSTIC TESTS .
- Ensure all mechanical engine systems other than computerized systems (i.e., compression, ignition, etc.) are operating properly. DO NOT proceed with testing unless all other problems have been repaired. If Malfunction Indicator Light (MIL) is on, see RETRIEVING DIAGNOSTIC TROUBLE CODES . For diagnosing DTCs, see appropriate DTC test under DIAGNOSTIC TROUBLE CODES .
- After repairs have been completed, clear DTC(s). See CLEARING DIAGNOSTIC TROUBLE CODES . Recheck system and verify repair is complete.
Use the Manual With the Right Hardware
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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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