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P0138 Infiniti Code - HO2S12 Circuit High Voltage

Quick Answer

The P0138 code in an Infiniti indicates that there is a high voltage condition in the HO2S12 (Heated Oxygen Sensor 1 Bank 1) circuit. Common causes include Faulty HO2S12 sensor, Damaged wiring or connectors in the sensor circuit, Issues with the ECM. 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 Infiniti indicates HO2S12 Circuit High Voltage.
Common causes
Common causes include Faulty HO2S12 sensor, Damaged wiring or connectors in the sensor circuit, Issues with the ECM.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 06, 2024
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Code P0138 Infiniti Description

The P0138 code in an Infiniti indicates that there is a high voltage condition in the HO2S12 (Heated Oxygen Sensor 1 Bank 1) circuit. The HO2S12 sensor is responsible for measuring the oxygen content in the exhaust gases and relaying this information to the engine control module (ECM) to adjust fuel delivery for optimal combustion. A high voltage reading from this sensor can be caused by a variety of issues, such as a faulty sensor, wiring problems, or issues with the ECM.

OBDII Code P0138 Infiniti - HO2S12 Circuit High Voltage
P0138 Infiniti Code - HO2S12 Circuit High Voltage

Common Causes of P0138 Infiniti

  1. Faulty HO2S12 sensor
  2. Damaged wiring or connectors in the sensor circuit
  3. Issues with the ECM
  4. Exhaust leaks near the sensor
  5. Contamination of the sensor with oil or coolant

Symptoms of P0138 Infiniti

  1. Decreased fuel efficiency
  2. Rough idling or stalling
  3. Engine hesitation during acceleration
  4. Engine misfires
  5. Illumination of the Check Engine Light

How to Fix P0138 Infiniti

  1. Use a scan tool to verify the P0138 code and identify the specific cause of the high voltage condition.
  2. Inspect the wiring and connectors in the HO2S12 circuit for any damage or corrosion, repairing or replacing as needed.
  3. Test the HO2S12 sensor using a multimeter to determine if it is functioning properly, replacing it if necessary.
  4. Clear the code and perform a test drive to ensure the issue has been resolved.
  5. If the problem persists, further diagnostics may be required to pinpoint the root cause of the high voltage condition.

Cost to Fix P0138 Infiniti

The cost of repairing a P0138 code in an Infiniti can vary depending on the specific cause of the issue. On average, the cost of parts for a new HO2S12 sensor ranges from $50 to $200, while labor costs can range from $100 to $200. Additional costs may be incurred if wiring repairs or ECM diagnostics are necessary. It's recommended to consult with a professional mechanic to get an accurate estimate for your specific vehicle.

What does this mean?

Tech Notes for P0138 Infiniti

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

When is the Code Detected?

The P0138 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.

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Information for Specific Infiniti Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0138 Infiniti Code

No Frequently Asked Questions about P0138 Infiniti Code found.

Discuss the causes and fixes for P0138 Infiniti OBDII Code

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  • Hello I have a 2001 infiniti g20 check code and the code is p0138
    I changed the O2 sensor and reset the engine light

    After driving approximately 40 miles light came back on
    Please help me solve this problem

    Thanks

    Reply to Comment

  • Did you used a factory Rear Oxygen Sensor or an aftermarket? did you got the same code P0138? are there any exhaust leaks?

    Reply to Comment

  • Hello Autocodes,
    I have p0138 and p0139
    I haven't replace the O2 B1S2 because I believe it's in good condition. I drive it for couple miles like the previous comment, engine light come up. Any suggestions or solution to solve this issue. Perhaps a video to start somewhere or an idea. I am knowledgeable with automotive. First case scenario, I fail smog check due to bad catalytic converter which is false in my point of view. Especially here in California Emission. Anyways, please reply

    Reply to Comment

  • What model and year is your Infiniti? how did you tested the O2 sensor?
    Unless there is an exhaust leak or the catalytic converter is not performing as designed, if you have the P0138 and P0139 code, the most likely cause of the problem is the Rear Oxygen Sensor

    Reply to Comment