AutoCodes – Mercedes-Benz – P0157 Mercedes-Benz

P0157 Mercedes-Benz Code - O2 Sensor Circuit Low Voltage 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: P0157 Mercedes-Benz indicates O2 Sensor Circuit Low Voltage 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 8,224

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 P0157 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 P0157 Mercedes-Benz - O2 Sensor Circuit Low Voltage Bank 2 Sensor 2 - AutoCodes.com — P0157 Mercedes-Benz Code - O2 Sensor Circuit Low Voltage Bank 2 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0157 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 P0157 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 P0157 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 P0157 Mercedes-Benz code?

Need more information on how to fix the P0157 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0157 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 P0157 Mercedes-Benz Code

1. What are the common symptoms of OBDII code P0157 in a Mercedes-Benz?

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

2. What does the OBDII code P0157, "O2 Sensor Circuit Low Voltage Bank 2 Sensor 2," mean in a Mercedes-Benz?

- This code indicates that the oxygen sensor located in the second bank of cylinders and downstream of the catalytic converter is reporting a voltage below the specified range.

3. What are the possible causes of OBDII code P0157 in a Mercedes-Benz?

- Potential causes include a faulty oxygen sensor, damaged wiring or connectors, exhaust leaks, a defective catalytic converter, or issues with the engine control module.

4. How can I diagnose the O2 sensor circuit low voltage issue in Bank 2 Sensor 2 in a Mercedes-Benz?

- Diagnosing this issue involves using an OBDII scanner to retrieve the code and then performing tests to check the oxygen sensor's voltage output, inspecting the wiring for damage, and ensuring proper connectivity.

5. Can I drive my Mercedes-Benz with the OBDII code P0157 present?

- It is not recommended to drive with this code present, as it can lead to decreased fuel efficiency and potentially cause damage to other components of the vehicle over time.

6. How can I repair OBDII code P0157 in my Mercedes-Benz?

- Repairing this code typically involves replacing the faulty oxygen sensor in Bank 2 Sensor 2 and addressing any underlying issues such as wiring damage or exhaust leaks.

7. Is it possible to reset the check engine light after fixing OBDII code P0157 in a Mercedes-Benz?

- Yes, the check engine light can be reset using an OBDII scanner after the issue causing the P0157 code has been resolved.

8. What are some tips to prevent OBDII code P0157 from reoccurring in my Mercedes-Benz?

- To prevent this code from reoccurring, it is essential to perform regular vehicle maintenance, address any exhaust leaks promptly, and ensure proper installation of components like oxygen sensors.

9. Can a DIY enthusiast fix OBDII code P0157 in a Mercedes-Benz, or should it be left to professionals?

- While some DIY enthusiasts may be able to replace the oxygen sensor themselves, diagnosing and repairing underlying issues may require professional expertise to ensure the problem is fully resolved.

10. How can I determine if the oxygen sensor in Bank 2 Sensor 2 of my Mercedes-Benz needs replacement?

- If the oxygen sensor is showing signs of physical damage, has a buildup of deposits, or is producing voltage readings outside of the specified range, it may need to be replaced to address the P0157 code.