AutoCodes – Mercedes-Benz – P0156 Mercedes-Benz

P0156 Mercedes-Benz Code - O2 Sensor Circuit Malfunction Bank 2 Sensor 2

Quick Answer

The heated oxygen sensor 2 (HO2S), 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 2, Rear Heated Oxygen Sensor Bank 2 harness is open or shorted, Rear Heated Oxygen Sensor Bank 2 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: P0156 Mercedes-Benz indicates O2 Sensor Circuit Malfunction Bank 2 Sensor 2.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 2, Rear Heated Oxygen Sensor Bank 2 harness is open or shorted, Rear Heated Oxygen Sensor Bank 2 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 16,831

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
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0156 Mercedes-Benz Description

The heated oxygen sensor 2 (HO2S), 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 P0156 Mercedes-Benz - O2 Sensor Circuit Malfunction Bank 2 Sensor 2 - AutoCodes.com — P0156 Mercedes-Benz Code - O2 Sensor Circuit Malfunction Bank 2 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0156 Mercedes-Benz?

Faulty Rear Heated Oxygen Sensor Bank 2
Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

How to Fix the DTC P0156 Mercedes-Benz?

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 2 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0156 Mercedes-Benz 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.

Need more information about the P0156 Mercedes-Benz code?

Need more information on how to fix the P0156 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0156 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area

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 Mercedes-Benz Code

1. What does the OBDII code P0156 for a Mercedes-Benz indicate?

The code P0156 indicates an O2 Sensor Circuit Malfunction for Bank 2 Sensor 2 in a Mercedes-Benz vehicle.

2. What are the common symptoms of a P0156 O2 sensor malfunction in a Mercedes-Benz?

Common symptoms include poor fuel efficiency, rough idling, engine misfires, and the illumination of the Check Engine Light.

3. What are the possible causes of a P0156 O2 sensor circuit malfunction in a Mercedes-Benz?

Potential causes include a faulty O2 sensor, damaged wiring or connectors, exhaust leaks, or issues with the engine's computer system.

4. How can I diagnose a P0156 code in my Mercedes-Benz?

Diagnosing the code involves using an OBDII scanner to read the code, inspecting the O2 sensor and its wiring for damage, checking for exhaust leaks, and testing the sensor's voltage output.

5. Can I drive my Mercedes-Benz with a P0156 O2 sensor circuit malfunction code?

It is not recommended to drive with a P0156 code as it can lead to poor engine performance and potentially cause further damage to the vehicle.

6. How can I repair a P0156 O2 sensor circuit malfunction in my Mercedes-Benz?

Repair options include replacing the faulty O2 sensor, repairing damaged wiring or connectors, fixing any exhaust leaks, and clearing the code with an OBDII scanner.

7. Are there any DIY tips for fixing a P0156 code in a Mercedes-Benz?

While some basic troubleshooting like checking for loose connections or damaged wires can be done by DIY enthusiasts, replacing the O2 sensor or more complex repairs may require professional assistance.

8. How much does it typically cost to repair a P0156 O2 sensor circuit malfunction in a Mercedes-Benz?

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

9. How often should the O2 sensors be replaced in a Mercedes-Benz to avoid P0156 code issues?

O2 sensors typically last around 100,000 miles, but it is recommended to follow the manufacturer's maintenance schedule and replace them as needed to prevent issues like the P0156 code.

10. Can a P0156 O2 sensor circuit malfunction code be related to other problems in a Mercedes-Benz?

Yes, other issues like fuel system problems, engine misfires, or exhaust leaks can sometimes trigger a P0156 code, so a thorough diagnosis is recommended to address any underlying issues.