AutoCodes – Volkswagen – P0155 Volkswagen

P0155 Volkswagen Code - HO2S21 Sensor Heater Circuit

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 Volkswagen indicates HO2S21 Sensor Heater Circuit.
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 10,006

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 Mar 23, 2024

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0155 Volkswagen 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. The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

OBDII Code P0155 Volkswagen - HO2S21 Sensor Heater Circuit - AutoCodes.com — P0155 Volkswagen Code - HO2S21 Sensor Heater Circuit

What does this mean?

What are the Possible Causes of the DTC P0155 Volkswagen?

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 Volkswagen?

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

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 take the sensor to warm up and start sending an adequate signal. The code means the 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 Volkswagen 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 Volkswagen Code

1. What does OBDII code P0155 for a Volkswagen indicate?

This code (P0155) refers to a malfunction in the HO2S21 sensor heater circuit, which is located in the second oxygen sensor on bank 2 of the engine.

2. What are the common symptoms of a P0155 error code in a Volkswagen?

Common symptoms include poor fuel economy, rough idling, engine hesitation, failed emissions test, and the illumination of the check engine light.

3. What are the possible causes of a P0155 HO2S21 sensor heater circuit fault in a Volkswagen?

Possible causes include a faulty oxygen sensor, damaged wiring or connectors, blown fuse, issues with the engine control module (ECM), or a problem with the sensor heater circuit itself.

4. How can I diagnose a P0155 error code in my Volkswagen?

Diagnosis typically involves checking the oxygen sensor wiring and connectors, testing the sensor heater circuit, inspecting the fuse, and using a diagnostic scanner to monitor sensor readings.

5. Can I drive my Volkswagen with a P0155 fault code?

It is not recommended to drive your vehicle with a P0155 fault code, as it can lead to poor engine performance and potentially cause further damage to the vehicle over time.

6. How can I repair a P0155 error code in my Volkswagen?

Repair options include replacing the oxygen sensor, repairing damaged wiring or connectors, checking and replacing the fuse if necessary, and resetting the fault code with a diagnostic scanner.

7. Is it safe to continue driving my Volkswagen if the check engine light is on due to a P0155 code?

It is best to address the issue promptly to prevent potential damage to the vehicle and ensure optimal engine performance. Continuing to drive with a P0155 fault can lead to decreased fuel efficiency and engine performance.

8. Can I reset the P0155 error code in my Volkswagen without fixing the issue?

While you can clear the fault code using a diagnostic scanner, it is essential to address the underlying problem causing the P0155 code to prevent it from reoccurring and potentially causing further issues.

9. How much does it typically cost to repair a P0155 fault code in a Volkswagen?

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, such as replacing the oxygen sensor or repairing wiring.

10. How often should I replace the oxygen sensors in my Volkswagen to prevent P0155 codes?

Oxygen sensors typically last around 60,000 to 90,000 miles, but it is recommended to follow the manufacturer's guidelines and have them inspected regularly to prevent issues like the P0155 code from occurring.