P0138 Mitsubishi Code - Cylinder 1-4 Heated Oxygen Rear Sensor Circuit High Voltage
Quick Answer
The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. 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 Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
- 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.
Code P0138 Mitsubishi Description
What are the Possible Causes of the DTC P0138 Mitsubishi?
- Faulty Rear Heated Oxygen Sensor Bank 1
- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
- Intake air leaks
- Exhaust gas leaks
- Inappropriate fuel pressure
- Faulty fuel injectors
How to Fix the DTC P0138 Mitsubishi?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0138 Mitsubishi code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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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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