AutoCodes – GMC – P0156 GMC

P0156 GMC Code - Heated Oxygen Sensor Circuit Malfunction Bank 2 Sensor 2

Quick Answer

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Common causes include Faulty Heated Oxygen Sensor Bank 2 Sensor 2, Heated Oxygen Sensor Bank 2 Sensor 2 harness is open or shorted, Heated Oxygen Sensor Bank 2 Sensor 2 circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0156 GMC indicates Heated Oxygen Sensor Circuit Malfunction Bank 2 Sensor 2.
Common causes: Common causes include Faulty Heated Oxygen Sensor Bank 2 Sensor 2, Heated Oxygen Sensor Bank 2 Sensor 2 harness is open or shorted, Heated Oxygen Sensor Bank 2 Sensor 2 circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 1,592

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

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

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0156 GMC Description

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach an operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in an open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and a closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream.
The HO2S bank 1 sensor 2 and HO2S bank 2 sensor 2 are used for catalyst monitoring. This diagnostic runs once per ignition cycle. This diagnostic consists of two tests, a passive test, and an intrusive test. During the passive test, if the HO2S bank 1 sensor 2 or HO2S bank 2 sensor 2 voltage transitions below 350 mV and above 709 mV, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test, the intrusive test will begin. During the intrusive test, the control module will force the air-to-fuel ratio rich and/or lean. The control module then waits for a predicted response from the HO2S. If the HO2S voltage transitions below 350 mV and/or above 709 mV, the DTC will pass for this ignition cycle. If the control module does not receive the expected response from the HO2S, DTC P0136 will set for HO2S bank 1 sensor 2 or DTC P0156 will set for HO2S bank 2 sensor 2.

OBDII Code P0156 GMC - Heated Oxygen Sensor Circuit Malfunction Bank 2 Sensor 2 - AutoCodes.com — P0156 GMC Code - Heated Oxygen Sensor Circuit Malfunction Bank 2 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0156 GMC?

Faulty Heated Oxygen Sensor Bank 2 Sensor 2
Heated Oxygen Sensor Bank 2 Sensor 2 harness is open or shorted
Heated Oxygen Sensor Bank 2 Sensor 2 circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P0156 GMC?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0156 GMC 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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Need Help with the Code?

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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 P0156 GMC Code

1. What are the common symptoms of P0156 GMC code?

- Common symptoms include poor fuel economy, rough idling, failed emissions test, and the check engine light coming on.

2. What does the P0156 GMC code indicate?

- The code indicates a malfunction in the heated oxygen sensor circuit for Bank 2 Sensor 2 in the vehicle's exhaust system.

3. What are the possible causes of the P0156 GMC code?

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

4. How can I diagnose the cause of the P0156 GMC code?

- Diagnose by using an OBDII scanner to retrieve the specific fault code, inspecting the oxygen sensor and related components, and checking for any visible damage or corrosion.

5. Can I continue driving with the P0156 GMC code present?

- It is not recommended to continue driving with the code present as it can lead to further engine damage and decreased fuel efficiency.

6. How can I repair the P0156 GMC code?

- Repair options include replacing the oxygen sensor, repairing damaged wiring or connectors, fixing exhaust leaks, or resetting the engine's computer.

7. Is it possible for a DIY enthusiast to fix the P0156 GMC code?

- Yes, some repairs related to the P0156 code can be done by a DIY enthusiast with the necessary tools and knowledge.

8. How much does it cost to repair the P0156 GMC code at a mechanic?

- The cost of repairs can vary depending on the cause of the code and the mechanic's labor rates, but it typically ranges from $100 to $400.

9. How long does it take to repair the P0156 GMC code?

- The repair time can vary based on the specific cause of the code and the complexity of the repair, but it can typically be done in a few hours to a day.

10. Can the P0156 GMC code reappear after repairs?

- Yes, the code can reappear if the underlying issue is not fully resolved, so it's important to ensure that all related components are properly fixed during the repair process.