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.
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HOMESERVICE MANUALSLEXUS1991ES 250 AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES
1991 Lexus ES 250 Automatic
Engine Controls - Tests W/Codes
1991 Lexus ES 250 AutomaticSECTION Engine Controls - Tests W/Codes
- Introduction
- Self-Diagnostic System
- Summary
- Trouble Code Charts
- Notes
- Code 12: Rpm Signal
- Code 13: Rpm Signal
- Code 14: Ignition Signal
- Code 16: ECT Control Signal
- Code 21: Main O2 Sensor Signal Or Heater Signal
- Code 22: Water Temperature Sensor Signal
- Code 24: Intake Air Temperature Sensor Signal
- Codes 25 & 26: Air/Fuel Ratio Lean Malfunction
- Code 27: Sub-O2 Sensor Signal (CALIF)
- Code 31 & 32: Airflow Meter Signal
- Code 41: Throttle Position Sensor (TPS) Signal
- Code 42: Vehicle Speed Sensor (VSS) Signal
- Code 43: Starter Signal
- Code 51: Switch Condition Signal
- Code 52: Knock Sensor Signal
- Code 53: Knock Control Signal
- Code 71: EGR System Malfunction (CALIF)
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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.