AutoCodes – Audi – P0155 Audi

P0155 Audi 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 Audi 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 12,060

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 Audi 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 Audi - HO2S21 Sensor Heater Circuit - AutoCodes.com — P0155 Audi Code - HO2S21 Sensor Heater Circuit

What does this mean?

What are the Possible Causes of the DTC P0155 Audi?

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 Audi?

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 Audi 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 Audi Code

1. What does the OBDII code P0155 for my Audi indicate?

- The OBDII code P0155 specifically refers to a fault in the HO2S21 sensor heater circuit, which is the oxygen sensor located after the catalytic converter.

2. What are the common symptoms of a P0155 error in an Audi?

- Common symptoms of a P0155 error in an Audi may include poor fuel economy, rough idling, hesitation or stalling, and an illuminated check engine light.

3. What are the possible causes of a P0155 code in an Audi?

- The P0155 code in an Audi can be triggered by a faulty HO2S21 sensor, damaged wiring or connectors in the sensor circuit, a blown fuse, or a malfunctioning engine control module (ECM).

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

- To diagnose a P0155 error in your Audi, you can use an OBDII scanner to retrieve the specific code, visually inspect the sensor and its wiring for any visible damage, and test the sensor's resistance and heater circuit.

5. Can I drive my Audi with a P0155 error code?

- It is not recommended to drive your Audi with a P0155 error code for an extended period, as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

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

- Repairing a P0155 error in your Audi may involve replacing the HO2S21 sensor, repairing or replacing damaged wiring or connectors, checking and replacing any blown fuses, or reprogramming the engine control module (ECM).

7. Is it possible to clear a P0155 error code in an Audi without fixing the issue?

- Clearing a P0155 error code without addressing the underlying issue is not recommended, as the problem causing the code will persist and may lead to further complications down the road.

8. How much does it typically cost to fix a P0155 error in an Audi?

- The cost of fixing a P0155 error in an Audi can vary depending on the specific cause of the issue, but it may range from $100 to $300 for parts and labor.

9. Can a DIY enthusiast repair a P0155 error in an Audi?

- While some DIY enthusiasts may have the skills to repair a P0155 error in an Audi, it is recommended to have the issue diagnosed and repaired by a professional mechanic to ensure proper resolution.

10. How often does a P0155 error occur in Audi vehicles?

- The occurrence of a P0155 error in Audi vehicles can vary, but it is not an uncommon issue and can be encountered due to factors like sensor wear, wiring issues, or ECM malfunctions.