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
1998 Lexus GS 300SECTION 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 Diagnostic Trouble Codes
Connect appropriate OBD-II scan tool. Retrieve codes and record any freeze-frame data. See RETRIEVING DIAGNOSTIC TROUBLE CODES . - Clear Trouble Codes
Clear codes using scan tool. See CLEARING DIAGNOSTIC TROUBLE CODES . - Perform 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 Diagnostic Trouble Codes
Perform diagnosis and repair procedures as needed. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION . 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 diagnostic trouble codes. See CLEARING DIAGNOSTIC TROUBLE CODES . Perform road test. Ensure no codes are present and all symptoms and/or complaints have been repaired.
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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.