Testing Procedure

1998 Lexus SC 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 CODESΒ .
  • Clear Trouble Codes

    Clear codes using scan tool. See CLEARING DIAGNOSTIC TROUBLE CODESΒ .
  • 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) IDENTIFICATIONΒ . 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 CODESΒ . 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:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.