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.
Engine Controls - Tests W/Codes - 4-CYL: Summary
If no hard fault codes are present (or only pass codes), driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
| Code | Diagnostic Hints | ||
|---|---|---|---|
| 11 | Momentary Interruption Of Power Supply To ECU | ||
| 12 | No "G" or "NE" (RPM) Ignition Signal To ECU Within 2 Seconds After Engine Is Cranked | ||
| 13 | No "NE" (RPM) Ignition Signal To ECU When Engine Speed Is Greater Than Approximately 1000 RPM | ||
| 14 | No "IGF" Ignition Signal To ECU From Ignitor Several Times In Succession | ||
| 16 | Fault In Transmission/Transaxle ECU | ||
| 21 | Defective O2 Sensor, Open Or Short Circuit In O2 Sensor Signal | ||
| 22 | Open Or Short Circuit In Coolant Temp. Sensor Signal | ||
| 24 | Open Or Short Circuit In Intake Air Temp. Sensor Signal | ||
| 25 | Lean Signal Sent By O2 Sensor For Several Seconds | ||
| 26 | Rich Signal Sent By O2 Sensor For Several Seconds | ||
| 27 | Open Or Short Circuit In Sub-O2 Sensor Signal | ||
| 28 | Defective No. 2 O2 Sensor, Open Or Short Circuit In No. 2 O2 Sensor Signal | ||
| 31 | Open Or Short Circuit In Airflow Meter Or Vacuum Sensor Signal | ||
| 32 | Open Or Short Circuit Between Airflow Meter Terminals | ||
| 34 | Turbocharger Pressure Is Abnormal | ||
| 35 | Open Or Short Circuit In Turbocharger Pressure Sensor Or High Altitude Compensator Signal | ||
| 41 | Open Or Short Circuit In Throttle Position Sensor Signal | ||
| 42 | No "SPD" Signal From Vehicle Speed Sensor For Several Seconds With Engine Speed Approximately 2500-5500 RPM | ||
| 43 | No "STA" Signal To ECU Until Engine Reaches 800 RPM With Vehicle Not Moving | ||
| 51 | (1) Problem In One Of 3 Circuits Monitored By ECU | ||
| 52 | Open Or Short Circuit In Knock Sensor Signal | ||
| 53 | Knock Control In ECU Is Faulty | ||
| 71 | EGR Gas Below Predetermined Level During EGR Control | ||
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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.