AutoCodes – Mercedes-Benz – P0155 Mercedes-Benz

P0155 Mercedes-Benz Code - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1

Quick Answer

Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground. 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: P0155 Mercedes-Benz indicates O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1.
Common causes: Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground.
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 22,636

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 Sep 12, 2019

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0155 Mercedes-Benz Description

Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM). In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.
This fault code is stored in the engine control module when the current flow through the oxygen sensor heater circuit is not as expected. The ECM uses a comparator to measure the voltage drop across a known resistor, using this value the system can calculate the current flow within the circuit. The supply voltage to the component must be investigated. The resistance of the heater element should also be tested. A resistance of approximately 8 Ohms to 15 Ohms is satisfactory. Due to the location of this component the electrical connector can become contaminated with splash from the road. Separate the electrical connector and inspect the pins for corrosion.

OBDII Code P0155 Mercedes-Benz - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 - AutoCodes.com — P0155 Mercedes-Benz Code - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1

What does this mean?

What are the Possible Causes of the DTC P0155 Mercedes-Benz?

Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1
Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse
Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground
Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0155 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

Mercedes Benz Code = 0437 (Left O2 sensor, before TWC): Short circuit to positive / Resistance of sensor heater too low (P0155)
Mercedes Benz Code = 0440 (Left O2 sensor, before TWC): Heating capacity is too low. (P0155)

The code means that there is a problem with the heater element circuit of the heated oxygen sensor. The Engine Control Module (ECM) monitors how long it takes the sensor to warm up and start sending an adequate signal. The code means the sensor is taking too long to warm up. Replacing the Front Heated Oxygen Sensor (H2OS) Bank 2 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0155 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.

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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 P0155 Mercedes-Benz Code

1. What does the OBDII code P0155 Mercedes-Benz mean?

The code P0155 indicates an O2 sensor heater circuit malfunction on Bank 2 Sensor 1 in a Mercedes-Benz vehicle.

2. What are the common symptoms of O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in a Mercedes-Benz?

Common symptoms include decreased fuel efficiency, rough idling, engine misfires, and the illumination of the check engine light.

3. What are the possible causes of the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in a Mercedes-Benz?

Possible causes may include a faulty O2 sensor, damaged wiring or connectors, a blown fuse, or issues with the engine control module.

4. How can I diagnose the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in my Mercedes-Benz?

Diagnosis involves using an OBDII scanner to retrieve the error code, inspecting the O2 sensor and its connections, and checking the related fuses for continuity.

5. Can I continue driving my Mercedes-Benz with the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) code?

It is not recommended to drive your vehicle with the P0155 code as it can lead to decreased performance and potential damage to the catalytic converter.

6. How do I repair the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in my Mercedes-Benz?

Repair typically involves replacing the faulty O2 sensor, repairing damaged wiring or connectors, or addressing any issues with the engine control module.

7. Are there any DIY tips for fixing the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in a Mercedes-Benz?

While some simple tasks like checking and replacing fuses can be done by DIY enthusiasts, it is recommended to have a qualified mechanic diagnose and repair this issue.

8. How much does it cost to repair the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in a Mercedes-Benz?

The cost of repair can vary depending on the specific issue and the labor rates in your area, but it typically ranges from $200 to $500 for parts and labor.

9. Will resetting the check engine light resolve the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) in my Mercedes-Benz?

Resetting the check engine light may temporarily turn it off, but it will not fix the underlying issue causing the P0155 code. It is important to diagnose and repair the problem to prevent further issues.

10. How often should the O2 sensors be inspected in a Mercedes-Benz to prevent O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1 (P0155) issues?

It is recommended to inspect the O2 sensors during regular maintenance intervals or whenever you experience symptoms like poor fuel efficiency or rough idling to prevent potential issues like the P0155 code.