P0138 Subaru Code - HO2S12 Circuit High Voltage
Quick Answer
The P0138 code for Subaru vehicles indicates a problem with the HO2S12 sensor, which is the oxygen sensor located downstream of the catalytic converter on bank 1. Common causes include Faulty HO2S12 sensor, Wiring issues in the sensor circuit, Exhaust leaks near the 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 Subaru indicates HO2S12 Circuit High Voltage.
- Common causes
- Common causes include Faulty HO2S12 sensor, Wiring issues in the sensor circuit, Exhaust leaks near the 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.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
Code P0138 Subaru Description
The P0138 code for Subaru vehicles indicates a problem with the HO2S12 sensor, which is the oxygen sensor located downstream of the catalytic converter on bank 1. The code specifically points to a high voltage condition in the sensor circuit. The oxygen sensor plays a crucial role in monitoring the oxygen levels in the exhaust gases to help the engine control module (ECM) adjust the air-fuel mixture for optimal combustion. When the sensor detects a high voltage, it means that the oxygen levels in the exhaust are too low, indicating a rich air-fuel mixture.
Common Causes of P0138 Subaru
- Faulty HO2S12 sensor
- Wiring issues in the sensor circuit
- Exhaust leaks near the sensor
- ECM malfunction
- Fuel system issues
Symptoms of P0138 Subaru
- Decreased fuel efficiency
- Rough idling or stalling
- Engine misfires
- Check Engine Light illuminated
- Increased emissions
How to Fix P0138 Subaru
- Use an OBD-II scanner to confirm the P0138 code and identify the specific issue.
- Inspect the wiring and connections in the HO2S12 sensor circuit for any damage or corrosion.
- Test the HO2S12 sensor using a multimeter to check for proper voltage output.
- Replace the HO2S12 sensor if it is found to be faulty.
- Clear the trouble codes and test drive the vehicle to ensure the issue has been resolved.
Cost to Fix P0138 Subaru
The cost of repairing a P0138 code on a Subaru can vary depending on the specific cause of the issue. In general, the cost of replacing an oxygen sensor can range from $100 to $300, including parts and labor. Additional costs may apply if wiring repairs or ECM diagnostics are needed. It's important to note that labor rates at auto repair shops can vary, so it's recommended to obtain quotes from multiple sources to get an accurate estimate for your specific vehicle.
Tech Notes for P0138 Subaru
When is the Code Detected?
Need more information about the P0138 Subaru code?
Need more information on how to fix the P0138 Subaru code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0138 Subaru code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P0138 Subaru Code
What does the OBDII code P0138 mean for a Subaru?
P0138 indicates high voltage in the downstream oxygen sensor (HO2S12), typically caused by issues with the sensor or related components.
What are common symptoms of P0138 on a Subaru?
Symptoms include reduced fuel efficiency, a check engine light, poor engine performance, and potentially an unusual smell from the exhaust.
What causes the P0138 code on a Subaru?
Common causes include a faulty downstream oxygen sensor, wiring issues, a short circuit, or an overly rich air-fuel mixture.
Can a dirty or clogged catalytic converter trigger the P0138 code?
Yes, a damaged or clogged catalytic converter can cause abnormal readings in the downstream oxygen sensor, leading to the P0138 code.
How do you diagnose the P0138 code in a Subaru?
Diagnosis involves inspecting the downstream oxygen sensor, checking for wiring damage, testing sensor voltage, and verifying proper air-fuel mixture levels.
Is it safe to drive a Subaru with the P0138 code?
While the vehicle may remain drivable, ignoring P0138 can lead to further damage, reduced fuel efficiency, and increased emissions.
How do you fix the P0138 code on a Subaru?
Repair may involve replacing the downstream oxygen sensor, fixing damaged wiring, or addressing issues with the catalytic converter or fuel system.
Can a vacuum leak cause the P0138 code?
No, vacuum leaks are unlikely to cause P0138, as this code relates specifically to high voltage in the downstream oxygen sensor circuit.
How much does it cost to fix the P0138 code on a Subaru?
The cost varies depending on the issue, with oxygen sensor replacement ranging from $100 to $300, including parts and labor.
Will clearing the P0138 code without repairs fix the issue permanently?
No, clearing the code without addressing the underlying problem will only temporarily reset the check engine light, and the issue will likely return.
Discuss the causes and fixes for P0138 Subaru OBDII Code
Code P0138 Subaru comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.