1990 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Basic Checks

  1. Ensure battery voltage is at least 11 volts with engine off. If battery voltage is not to specification, replace battery. If battery voltage is to specification, go to next step.
  2. Crank engine. If engine cranks, go to next step. If engine does not crank, see in DIAGNOSIS BY SYMPTOM in appropriate TESTS W/O CODES article.
  3. Start engine. If engine starts, go to next step. If engine does not start, go to step 12).
  4. Remove air filter. Inspect air filter for excessive dirt and oil. Replace if necessary. Reinstall air filter if okay and go to next step.
  5. Check air intake system between airflow meter and cylinder head for air leaks. If air leaks are found, repair as necessary. If no air leaks are found, go to next step.
  6. Check idle speed. Start and warm engine to operating temperature. Place transmission in Neutral. Turn off all accessories. Connect a tachometer to terminal IG- of check connector. For location of check connector, see Fig 1.
  7. Set tachometer to 4-cylinder scale. See IDLE SPEED SPECIFICATIONS table. If idle speed is okay, go to next step. If idle speed is not within specification, see DIAGNOSIS BY SYMPTOM in appropriate TESTS W/O CODES article.
    CAUTION: DO NOT ground check connector terminal IG-. Damage to ignitor and/or ignition coil may result.
Factory Service Tools

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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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