AutoCodes – MINI – P0138 MINI

P0138 MINI Code - O2 Sensor Circuit High Voltage Bank 1 Sensor 2

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 MINI indicates O2 Sensor Circuit High Voltage Bank 1 Sensor 2.
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.

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Code Popularity 17,051

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0138 MINI Description

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. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0138 MINI - O2 Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 MINI Code - O2 Sensor Circuit High Voltage Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0138 MINI?

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 MINI?

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.

What does this mean?

Code Tech Notes

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

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 MINI 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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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 MINI Code

1. What are the common symptoms of OBDII code P0138 in a MINI, indicating an issue with the O2 Sensor Circuit High Voltage Bank 1 Sensor 2?

- Common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and the illumination of the check engine light.

2. What are the possible causes of O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in a MINI?

- Possible causes include a faulty oxygen sensor, damaged wiring or connector, exhaust leaks, or issues with the engine's computer.

3. How can I diagnose the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in my MINI?

- Diagnose the issue by using an OBDII scanner to retrieve the trouble code, inspecting the sensor and its wiring for damage, and checking for any exhaust leaks.

4. Can a dirty or contaminated sensor cause O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in a MINI?

- Yes, a dirty or contaminated sensor can cause false readings and trigger the P0138 code. Cleaning or replacing the sensor may resolve the issue.

5. What are some repair tips for addressing the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in a MINI?

- Repair tips include replacing the oxygen sensor, repairing or replacing damaged wiring, fixing any exhaust leaks, and resetting the check engine light after repairs.

6. Is it safe to continue driving my MINI with the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) unresolved?

- It is not recommended to drive your MINI with the P0138 code unresolved, as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

7. How much does it typically cost to repair the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in a MINI?

- The cost of repair can vary depending on the underlying cause, but it may range from $100 to $300 for parts and labor.

8. Can I reset the check engine light after repairing the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) in my MINI?

- Yes, you can reset the check engine light using an OBDII scanner after addressing the P0138 code. If the issue is fixed, the light should stay off.

9. How often should the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 be checked and replaced in a MINI?

- O2 sensors typically have a lifespan of 50,000 to 100,000 miles. It's recommended to check and replace them as needed during regular maintenance intervals.

10. Will driving with the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 issue (P0138) affect my MINI's emissions or performance?

- Driving with the P0138 code unresolved can impact your MINI's emissions levels and performance, potentially leading to higher emissions and reduced engine efficiency.