P0138 Mitsubishi Code - Cylinder 1-4 Heated Oxygen Rear Sensor Circuit High Voltage
Quick Answer
The P0138 diagnostic trouble code for Mitsubishi vehicles indicates an issue with the Cylinder 1-4 Heated Oxygen Rear Sensor Circuit High Voltage. Common causes include Faulty oxygen sensor: The most common cause of this code is a malfunctioning oxygen sensor that is sending incorrect voltage readings to the ECM, Wiring issues: Damaged or corroded wiring connections between the oxygen sensor and ECM can disrupt the signal and cause high voltage readings, Exhaust leaks: Leaks in the exhaust system can introduce excess oxygen into the exhaust gases, leading to false high voltage readings from the oxygen sensor. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
- What it means
- P0138 Mitsubishi indicates Cylinder 1-4 Heated Oxygen Rear Sensor Circuit High Voltage.
- Common causes
- Common causes include Faulty oxygen sensor: The most common cause of this code is a malfunctioning oxygen sensor that is sending incorrect voltage readings to the ECM, Wiring issues: Damaged or corroded wiring connections between the oxygen sensor and ECM can disrupt the signal and cause high voltage readings, Exhaust leaks: Leaks in the exhaust system can introduce excess oxygen into the exhaust gases, leading to false high voltage readings from the oxygen sensor.
- Severity
- Moderate - service should be scheduled soon.
- Can I drive?
- The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
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Code P0138 Mitsubishi Description
The P0138 diagnostic trouble code for Mitsubishi vehicles indicates an issue with the Cylinder 1-4 Heated Oxygen Rear Sensor Circuit High Voltage. This means that there is a higher than normal voltage reading detected in the rear oxygen sensor of cylinders 1 to 4. The oxygen sensor, also known as the O2 sensor, plays a crucial role in monitoring the amount of oxygen in the exhaust gases and helping to adjust the air-fuel mixture for optimal engine performance.
Common Causes of P0138 Mitsubishi
- Faulty oxygen sensor: The most common cause of this code is a malfunctioning oxygen sensor that is sending incorrect voltage readings to the ECM.
- Wiring issues: Damaged or corroded wiring connections between the oxygen sensor and ECM can disrupt the signal and cause high voltage readings.
- Exhaust leaks: Leaks in the exhaust system can introduce excess oxygen into the exhaust gases, leading to false high voltage readings from the oxygen sensor.
- Engine running rich: Issues such as a malfunctioning fuel injector or a faulty fuel pressure regulator can cause the engine to run rich, resulting in high voltage readings from the oxygen sensor.
Symptoms of P0138 Mitsubishi
- Decreased fuel efficiency: A high voltage reading from the oxygen sensor can cause the engine to run rich, leading to decreased fuel economy.
- Check Engine Light: The illumination of the check engine light on the dashboard is a common symptom of this code being triggered.
- Rough idling: An irregular or rough idling engine may occur due to the incorrect air-fuel mixture caused by the malfunctioning oxygen sensor.
- Engine misfires: The engine may experience misfires or hesitations during acceleration or while driving.
How to Fix P0138 Mitsubishi
- Diagnostic scan: Begin by using an OBD-II scanner to retrieve the specific trouble code and confirm the issue with the oxygen sensor.
- Check wiring: Inspect the wiring harness and connectors for any damage, corrosion, or loose connections. Repair or replace as necessary.
- Replace oxygen sensor: If the oxygen sensor is faulty, it will need to be replaced with a new sensor that meets the manufacturer's specifications.
- Clear codes: After completing the repair, clear the diagnostic trouble codes from the ECM memory using the OBD-II scanner.
- Test drive: Take the vehicle for a test drive to ensure that the repair has resolved the issue and that the check engine light does not reappear.
Cost to Fix P0138 Mitsubishi
The cost of repairing the P0138 code for a Mitsubishi vehicle can vary depending on the specific model and the labor rates in your area. On average, the cost of replacing an oxygen sensor ranges from $200 to $300, including parts and labor. However, additional costs may apply if there are wiring issues or other underlying problems contributing to the code. It is recommended to consult with a trusted mechanic or auto repair shop for an accurate cost estimate based on your vehicle's needs. Labor rates at auto repair shops typically range from $80 to $150 per hour, but can vary based on location and shop.
Tech Notes for P0138 Mitsubishi
When is the Code Detected?
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Frequently Asked Questions about P0138 Mitsubishi Code
1. What does the OBDII code P0138 mean for a Mitsubishi?
P0138 indicates that the heated oxygen sensor (rear sensor) for cylinders 1-4 is detecting a high voltage, which typically means there’s an issue with the sensor or its circuit.
2. What are the common symptoms of code P0138 on a Mitsubishi?
Symptoms may include poor fuel economy, rough idling, engine hesitation, or an illuminated check engine light.
3. What causes code P0138 to appear on a Mitsubishi?
Common causes include a faulty oxygen sensor, damaged wiring or connectors, exhaust leaks, or an overly rich air-fuel mixture.
4. Can I drive my Mitsubishi with code P0138?
While it may be possible to drive, doing so can lead to reduced performance, increased emissions, and potential damage to the catalytic converter.
5. How do I diagnose code P0138 on a Mitsubishi?
Use an OBDII scanner to confirm the code, visually inspect the oxygen sensor and wiring, and check for exhaust or fuel system issues.
6. How is code P0138 fixed on a Mitsubishi?
Repairs may include replacing the oxygen sensor, fixing damaged wires or connectors, addressing exhaust leaks, or correcting fuel system imbalances.
7. How much does it cost to repair code P0138 on a Mitsubishi?
Repair costs vary but typically range from $150 to $300 for sensor replacement, depending on parts and labor.
8. Can a dirty or contaminated oxygen sensor cause code P0138?
Yes, contamination from oil or coolant leaks can affect the sensor's performance and trigger the code.
9. Will resetting the check engine light fix code P0138 on a Mitsubishi?
Resetting the light may temporarily clear the code, but the underlying issue must be resolved to prevent it from returning.
10. Is code P0138 related to the catalytic converter on a Mitsubishi?
While not directly caused by the catalytic converter, prolonged issues with the oxygen sensor can lead to catalytic converter damage.
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