Engine-CodesSubaru – P0159 Subaru

P0159 Subaru Code - HO2S22 Circuit Slow Response

Quick Answer

The P0159 Subaru diagnostic trouble code indicates a problem with the HO2S22 (Heated Oxygen Sensor 2 Sensor 2) circuit, specifically a slow response from the sensor. Common causes include Faulty HO2S22 sensor, Wiring or connector issues, Exhaust leaks near the sensor. 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
P0159 Subaru indicates HO2S22 Circuit Slow Response.
Common causes
Common causes include Faulty HO2S22 sensor, Wiring or connector issues, Exhaust leaks near the sensor.
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.
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0159 Subaru Description

The P0159 Subaru diagnostic trouble code indicates a problem with the HO2S22 (Heated Oxygen Sensor 2 Sensor 2) circuit, specifically a slow response from the sensor. The HO2S22 is responsible for monitoring the oxygen content in the exhaust gases and providing feedback to the engine control module (ECM) to adjust the air-fuel mixture for optimal combustion. When the sensor responds slowly or inaccurately, it can lead to issues with fuel efficiency, emissions, and overall engine performance.

OBDII Code P0159 Subaru - HO2S22 Circuit Slow Response
P0159 Subaru Code - HO2S22 Circuit Slow Response

Common Causes of P0159 Subaru

  1. Faulty HO2S22 sensor
  2. Wiring or connector issues
  3. Exhaust leaks near the sensor
  4. Rich or lean fuel mixture
  5. ECM software issues

Symptoms of P0159 Subaru

  1. Decreased fuel efficiency
  2. Engine hesitation or stumbling
  3. Rough idling or stalling
  4. Check Engine Light illuminated

How to Fix P0159 Subaru

  1. Diagnose the specific cause of the slow response (sensor, wiring, leaks, etc.)
  2. Replace the HO2S22 sensor if faulty
  3. Repair or replace damaged wiring or connectors
  4. Check and repair any exhaust leaks near the sensor
  5. Clear the trouble code and perform a test drive to ensure the issue is resolved

Cost to Fix P0159 Subaru

The cost estimate for repairing a P0159 Subaru code can vary depending on the specific cause of the issue. On average, replacing a HO2S22 sensor can cost between $100 and $200, while addressing wiring or connector issues may range from $50 to $150. Additional costs for diagnostic time and labor should be factored in, with total repair costs potentially ranging from $200 to $500. It's recommended to consult with a trusted mechanic or auto repair shop for a more accurate estimate based on the vehicle's make and model, as well as the local labor rates.

Tech Notes for P0159 Subaru

Replacing the O2 Sensor 2 usually takes care of the problem

When is the Code Detected?

The P0159 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor takes more time to respond between rich and lean than the specified time.

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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 P0159 Subaru Code

1. What are the common symptoms of OBDII code P0159 in a Subaru?

The common symptoms of code P0159 in a Subaru include poor fuel economy, rough idling, engine misfires, and the illumination of the Check Engine Light.

2. What does the OBDII code P0159 indicate for a Subaru?

Code P0159 indicates a slow response from the HO2S22 sensor, which is the oxygen sensor located after the catalytic converter.

3. What are the possible causes of OBDII code P0159 in a Subaru?

Common causes of code P0159 in a Subaru include a faulty HO2S22 sensor, wiring issues in the sensor circuit, exhaust leaks, or a problem with the catalytic converter.

4. How can I diagnose the OBDII code P0159 in my Subaru?

Diagnosing code P0159 involves using an OBDII scanner to read the code, checking the wiring and connections to the HO2S22 sensor, inspecting the sensor for damage, and testing the sensor's response time.

5. Can a dirty or contaminated sensor cause OBDII code P0159 in a Subaru?

Yes, a dirty or contaminated HO2S22 sensor can cause a slow response and trigger code P0159 in a Subaru. It is essential to clean or replace the sensor if contamination is found.

6. Is it safe to continue driving my Subaru with OBDII code P0159 present?

While the car may still be drivable with code P0159, it is recommended to address the issue promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

7. How can I repair OBDII code P0159 in my Subaru?

Repairing code P0159 may involve replacing the HO2S22 sensor, repairing damaged wiring or connections, fixing any exhaust leaks, or addressing issues with the catalytic converter.

8. Will resetting the Check Engine Light resolve OBDII code P0159 in a Subaru?

Simply resetting the Check Engine Light may temporarily clear the code, but it will likely return if the underlying issue causing code P0159 is not fixed.

9. Can a DIY enthusiast fix OBDII code P0159 in a Subaru?

Depending on their skill level, a DIY enthusiast may be able to address code P0159 by following repair guides, but it is recommended to consult a professional mechanic for accurate diagnosis and repair.

10. How much does it cost to repair OBDII code P0159 in a Subaru?

The cost of repairing code P0159 in a Subaru can vary depending on the specific issue causing the code, the cost of parts needed, and the labor rates of the mechanic. It is advisable to obtain quotes from different repair shops for an accurate estimate.

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