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.
1990 Lexus LS 400FACTORY OEM SERVICE PROCEDURE
No Lock-Up
- Check solenoid No. 3 circuit. See CODE 64 in TESTS W/CODES article.
- Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
- Check stoplight switch circuit. See STOPLIGHT SWITCH CIRCUIT chart in TESTS W/CODES article.
- Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
- Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
- Check neutral start switch circuit. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
- Check water temperature sensor. See CODE 22 in TESTS W/CODES article.
- Check transmission for mechanical failure.
- Check ECU. See SYSTEM/COMP TESTS article.
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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