AutoCodes – Subaru – P0159 Subaru

P0159 Subaru Code - HO2S22 Circuit Slow Response

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: P0159 Subaru indicates HO2S22 Circuit Slow Response.
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 6,806

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 P0159 Subaru 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 P0159 Subaru - HO2S22 Circuit Slow Response - AutoCodes.com — P0159 Subaru Code - HO2S22 Circuit Slow Response

What does this mean?

What are the Possible Causes of the DTC P0159 Subaru?

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 P0159 Subaru?

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 O2 Sensor 2 usually takes care of the problem

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0159 Subaru 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 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.