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P0155 Mitsubishi Code - HO2S 21 Heater Performance

Quick Answer

The P0155 code for Mitsubishi vehicles specifically refers to an issue with the HO2S (Heated Oxygen Sensor) 2, Bank 2. Common causes include Faulty Oxygen Sensor: The most common cause of the P0155 code is a faulty HO2S 21 sensor itself, Wiring Issues: Damaged or corroded wiring in the sensor's heater circuit can prevent the heater from functioning properly, Blown Fuse: A blown fuse in the oxygen sensor circuit can also trigger this code. 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 Mitsubishi indicates HO2S 21 Heater Performance.
Common causes
Common causes include Faulty Oxygen Sensor: The most common cause of the P0155 code is a faulty HO2S 21 sensor itself, Wiring Issues: Damaged or corroded wiring in the sensor's heater circuit can prevent the heater from functioning properly, Blown Fuse: A blown fuse in the oxygen sensor circuit can also trigger this code.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0155 Mitsubishi Description

The P0155 code for Mitsubishi vehicles specifically refers to an issue with the HO2S (Heated Oxygen Sensor) 2, Bank 2. This code indicates that there is a problem with the performance of the heater circuit of the oxygen sensor located in the exhaust system. The HO2S plays a crucial role in monitoring the oxygen levels in the exhaust gases and providing feedback to the engine control module (ECM) for optimal fuel delivery and emissions control.

OBDII Code P0155 Mitsubishi - HO2S 21 Heater Performance
P0155 Mitsubishi Code - HO2S 21 Heater Performance

Common Causes of P0155 Mitsubishi

  1. Faulty Oxygen Sensor: The most common cause of the P0155 code is a faulty HO2S 21 sensor itself.
  2. Wiring Issues: Damaged or corroded wiring in the sensor's heater circuit can prevent the heater from functioning properly.
  3. Blown Fuse: A blown fuse in the oxygen sensor circuit can also trigger this code.
  4. ECM Malfunction: A malfunction in the engine control module can prevent the proper operation of the oxygen sensor heater circuit.

Symptoms of P0155 Mitsubishi

  1. Check Engine Light: The most common symptom associated with the P0155 code is the illumination of the Check Engine Light on the vehicle's dashboard.
  2. Poor Fuel Efficiency: A malfunctioning HO2S heater can lead to inaccurate readings, causing the engine to run rich or lean, resulting in poor fuel efficiency.
  3. Rough Idle: The engine may experience rough idling or hesitation when the HO2S is not functioning properly.
  4. Failed Emissions Test: If the oxygen sensor is not working correctly, it can result in increased emissions, causing the vehicle to fail emissions tests.

How to Fix P0155 Mitsubishi

  1. Diagnose the Issue: Use an OBD-II scanner to retrieve the specific fault code and verify the problem with the HO2S 21 heater circuit.
  2. Inspect Wiring and Connections: Check the wiring and connections related to the oxygen sensor for any damage or corrosion. Repair or replace as necessary.
  3. Test Oxygen Sensor: Test the functionality of the HO2S 21 sensor to determine if it is faulty and needs replacement.
  4. Check Fuse: Inspect the fuse related to the oxygen sensor heater circuit and replace if blown.
  5. Reset the Code: Once the issue is resolved, clear the fault code using the OBD-II scanner to reset the Check Engine Light.

Cost to Fix P0155 Mitsubishi

The cost of repairing the HO2S 21 heater performance issue can vary depending on the specific cause of the problem and the labor rates at the auto repair shop. On average, the cost of replacing an oxygen sensor ranges from $200 to $300, including parts and labor. However, if the issue is related to wiring or fuse problems, the cost may be lower. It's recommended to consult with a mechanic or dealership for a more accurate estimate based on the specific diagnosis of the problem. Keep in mind that labor rates can vary, with most shops charging between $80 and $150 per hour for diagnostic and repair services.

What does this mean?

Tech Notes for P0155 Mitsubishi

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.

When is the Code Detected?

The current amperage in the front heated oxygen sensor heater circuit is out of the normal range. (An improper voltage drop signal is sent to ECM through the front heated oxygen sensor heater)

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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 Mitsubishi Code

What does the OBDII code P0155 mean for a Mitsubishi vehicle?

1. P0155 indicates an issue with the heater circuit of the oxygen sensor (HO2S) located on Bank 2, Sensor 1, meaning it is not heating up properly for accurate readings. 2.

What are the common symptoms of code P0155?

Symptoms may include an illuminated check engine light, decreased fuel efficiency, rough idling, poor engine performance, or increased exhaust emissions. 3.

What causes the P0155 code to appear on a Mitsubishi?

Common causes include a faulty Bank 2, Sensor 1 oxygen sensor, a blown fuse for the heater circuit, damaged wiring or connectors, or an issue with the engine control module (ECM). 4.

Can I drive my Mitsubishi with the P0155 code active?

Driving with P0155 may not cause immediate damage, but prolonged issues can lead to poor performance, increased emissions, and potential damage to the catalytic converter. 5.

How do I diagnose the P0155 code in my Mitsubishi?

Start by checking the oxygen sensor's heater circuit wiring and connectors for damage, test the sensor's resistance, and inspect the fuse for the heater circuit. 6.

How do I fix the P0155 code on a Mitsubishi?

Repairs may involve replacing the faulty oxygen sensor, repairing or replacing damaged wiring, replacing a blown fuse, or reprogramming the ECM if necessary. 7.

How much does it cost to fix the P0155 code?

The cost ranges from $150 to $300 for parts and labor to replace the oxygen sensor, but wiring or ECM repairs may vary based on the extent of the issue. 8.

Can a dirty oxygen sensor cause the P0155 code?

A dirty sensor is unlikely to cause P0155, as this code specifically relates to the heater circuit performance rather than sensor contamination. 9.

Is a special tool required to diagnose or fix the P0155 code?

Yes, a scan tool or OBDII code reader is needed to diagnose and clear the code, and a multimeter may be required to test the sensor and wiring. 10.

What happens if the P0155 code is ignored?

Ignoring the P0155 code can lead to decreased fuel efficiency, higher emissions, potential damage to the catalytic converter, and failed emissions tests.

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