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.
1993 Toyota Tercel BaseFACTORY OEM SERVICE PROCEDURE
Trouble Code Identification
| CODE No. | System Affected | MIL inNORMAL MODE | MIL in TEST MODE | Probable Cause | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 12 | RPM Signal | ON | - | Distributor, Starter or Ckt, ECM | ||||||||
| 13 | RPM Signal | ON | - | Distributor or Ckt, ECM | ||||||||
| 14 | Ignition Signal | ON | - | Ignitor or Ckt to ECM. ECM | ||||||||
| 21 | O2 Sensor Signal | ON | - | O2 Sensor or Ckt, ECM | ||||||||
| 22 | Coolant Temp. Sensor Signal | ON | - | Coolant Temp. Sensor or Ckt, ECM | ||||||||
| 24 | Intake Air Temp. Sensor Signal | ON (3) | - | Intake Air Temp. Sensor or Ckt, ECM | ||||||||
| 25 | Lean Air/Fuel Mixture | ON | - | Loose Ground, Injector or Ckt, Fuel Pressure, Ignition System, Coolant Temp. Sensor,Airflow Meter, Vacuum Sensor,O2 Sensor or Ckt, CompressionPressure, ECM | ||||||||
| 26 (3) | Rich Air/Fuel Mixture | ON | - | Loose Ground, Injector or Ckt, Fuel Pressure, Ignition System, Coolant Temp. Sensor,Airflow Meter, Vacuum Sensor,O2 Sensor or Ckt, Cold Start Injector or Ckt, Compression Pressure, ECM | ||||||||
| 31 | Vacuum Sensor Signal | ON | - | Vacuum Sensor or Ckt, ECM | ||||||||
| 41 | TPS Signal | ON (3) | - | Throttle Position Sensor or Ckt, ECM | ||||||||
| 42 | Vehicle Speed Sensor Signal | OFF | - | Vehicle Speed Sensor or Ckt, ECM | ||||||||
| 43 | Starter Signal | OFF | - | Starter Signal Ckt, Main Relay, Ignition Switch or Ckt, ECM | ||||||||
| 51 | Switch Condition Signal | OFF | - | A/C Switch, Park/Neutral Switch or Ckt, TPS or Ckt, ECM | ||||||||
| 71 (4) | EGR System Malfunction | ON | - | EGR System, EGR Temp. Sensor or Ckt, EGR-VSV, ECM | ||||||||
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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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