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.
Testing Procedure
To ensure correct diagnosis and repair, testing should be done in the following sequence:
- Record Customer Complaint Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification.
- Retrieve Trouble Codes Connect appropriate OBD-II scan tester. Retrieve codes and record any freeze-frame data. See RETRIEVING TROUBLE CODES .
- Clear Trouble Codes Clear codes using scan tester. See CLEARING TROUBLE CODES .
- Visual Inspection Inspect all connectors of suspect circuit or component. Ensure all connections are clean and tight.
- Confirm Symptoms & Trouble Codes Perform road test. Determine if original symptoms are still present. Retrieve codes.
- Diagnose & Repair Trouble Codes Perform diagnosis and repair procedures as needed. See appropriate DIAGNOSTIC TESTING. If no codes are present, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
- Verification Procedure
After repairs have been completed, clear all trouble codes. See CLEARING TROUBLE CODES . Perform road test. Ensure no trouble codes are present and all symptoms and/or complaints have been repaired.
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.