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.
1992 Lexus SC 400FACTORY OEM SERVICE PROCEDURE
Engine Controls - Tests W/Codes
- Introduction
- Self-Diagnostic System
- Diagnostic Code Charts
- Code 12, 17 & 18 - Rpm Signal Circuits
- Code 13 - Rpm Signal Circuit No. 2
- Code 14 & 15 - Ignition Signal (LS400)
- Code 14 & 15 - Ignition Signal (SC400)
- Code 16 - ECT Control Signal
- Code 21 & 28 - Main Oxygen Sensor Signal
- Code 22 - Water Temperature Sensor Signal
- Code 24 - Intake Air Temperature Sensor Signal
- Code 25 & 26 - Air/Fuel Ratio Lean Or Rich Signal
- Code 27 & 29 - Sub-Main Oxygen Sensor Circuit (LS400)
- Code 27 & 29 - Sub-Main Oxygen Sensor Circuit (SC400)
- Code 31 - Airflow Meter Signal
- Code 35 - High Altitude COMPENSATOR (HAC) Sensor Signal
- Code 41 & 47 - Throttle Position Sensor (TPS) Signal & Sub-Throttle Position Sensor Signal
- Code 42 - Vehicle Speed Sensor (VSS) Circuit (SC400)
- Code 43 - Starter Signal
- Code 51 - Switch Condition Signal (LS400)
- Code 51 - Switch Condition Signal (SC400)
- Code 52, 53 & 55 - Knock Sensor
- Code 71 - EGR System Malfunction (LS400)
- Code 71 - EGR System Malfunction (SC400)
- Code 78 - Fuel Pump Control Circuit (SC400)
- Summary
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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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