AutoCodes – Chevrolet – P0138 Chevrolet

P0138 Chevrolet Code - HO2S Circuit High Voltage Bank 1 Sensor 2

Quick Answer

The Heated Oxygen Sensors (HO2S) are used for fuel control and catalyst monitoring. 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 Chevrolet indicates HO2S 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 47,309

How popular is this code, among other codes? Medium

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 Oct 03, 2023

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

The Heated Oxygen Sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the Engine Control Module (ECM) operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0 - 1, 000 mV. Once sufficient HO2S voltage fluctuation is observed by the ECM, Closed Loop is entered. The ECM uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases toward 1, 000 mV indicates a rich fuel mixture. An HO2S voltage that decreases toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the ECM to calculate the air-to-fuel ratio sooner.
The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the HO2S voltage is greater than 1, 050 mV.

OBDII Code P0138 Chevrolet - HO2S Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 Chevrolet Code - HO2S Circuit High Voltage Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0138 Chevrolet?

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
Low or high fuel system pressure
Fuel contamination
Faulty fuel injectors
Exhaust gas leaks
Engine vacuum leaks

How to Fix the DTC P0138 Chevrolet?

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 (HO2S) Bank 1 usually takes care of the problem.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 Chevrolet 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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Information for Specific Chevrolet Models

P0138 2014 Chevrolet Silverado — HO2S Circuit High Voltage Bank 1 Sensor 2
P0138 2015 Chevrolet Silverado — HO2S Circuit High Voltage Bank 1 Sensor 2
P0138 2016 Chevrolet Silverado — HO2S Circuit High Voltage Bank 1 Sensor 2
P0138 2017 Chevrolet Silverado — HO2S Circuit High Voltage Bank 1 Sensor 2
P0138 2018 Chevrolet Silverado — HO2S Circuit High Voltage Bank 1 Sensor 2

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 Chevrolet Code

1. What are the common symptoms of OBDII code P0138 on a Chevrolet related to the HO2S Circuit High Voltage Bank 1 Sensor 2?

The common symptoms include the check engine light being illuminated on the dashboard, poor fuel economy, rough idling, and potential difficulty starting the vehicle.

2. What are the possible causes of OBDII code P0138 on a Chevrolet indicating HO2S Circuit High Voltage Bank 1 Sensor 2?

Possible causes include a faulty oxygen sensor, wiring issues in the sensor circuit, a vacuum leak, exhaust system leaks, or a problem with the engine's fuel system.

3. How can I diagnose the OBDII code P0138 on a Chevrolet for the HO2S Circuit High Voltage Bank 1 Sensor 2?

Diagnosis typically involves using an OBDII scanner to retrieve the specific trouble code, inspecting the oxygen sensor and its wiring for any visible damage, and checking for leaks in the exhaust system.

4. Can I drive my Chevrolet with the OBDII code P0138 related to HO2S Circuit High Voltage Bank 1 Sensor 2?

It is not recommended to drive the vehicle with this code present, as it can lead to poor engine performance and potentially cause further damage if left unchecked.

5. How can I repair OBDII code P0138 on a Chevrolet for the HO2S Circuit High Voltage Bank 1 Sensor 2?

Repair options may include replacing the oxygen sensor, repairing any damaged wiring, fixing exhaust leaks, addressing vacuum leaks, or resolving issues with the fuel system.

6. What are the potential long-term effects of ignoring OBDII code P0138 on a Chevrolet indicating HO2S Circuit High Voltage Bank 1 Sensor 2?

Ignoring this code can result in decreased fuel efficiency, engine misfires, potential damage to the catalytic converter, and overall poor engine performance.

7. How much does it typically cost to repair OBDII code P0138 on a Chevrolet related to HO2S Circuit High Voltage Bank 1 Sensor 2?

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

8. Can a DIY enthusiast fix OBDII code P0138 on a Chevrolet for the HO2S Circuit High Voltage Bank 1 Sensor 2?

Depending on their skill level, a DIY enthusiast may be able to address some aspects of the repair, such as replacing the oxygen sensor or checking for visible wiring issues. However, more complex diagnostics and repairs may require professional assistance.

9. Will resetting the check engine light resolve OBDII code P0138 on a Chevrolet indicating HO2S Circuit High Voltage Bank 1 Sensor 2?

Simply resetting the check engine light will not fix the underlying issue causing the trouble code. It is essential to diagnose and repair the root cause to prevent the code from reoccurring.

10. Can extreme weather conditions affect OBDII code P0138 on a Chevrolet related to HO2S Circuit High Voltage Bank 1 Sensor 2?

Extreme weather conditions, such as extreme heat or cold, can potentially impact the performance of the oxygen sensor and the sensor circuit, leading to the triggering of this trouble code.