P0055 Fault Code

P0055 OBD-II Trouble Code Short Description

HO2S Heater Resistance (Bank 1, Sensor 3)

What does trouble code P0055 mean?

The P0055 fault code refers to a problem with the HO2S (Heated Oxygen Sensor) heater resistance in Bank 1, Sensor 3. This sensor is located downstream (after) the catalytic converter in the exhaust system of the vehicle.

The oxygen sensor's function is to measure the amount of oxygen in the exhaust gases and allow the engine control module (ECM) to adjust the air-fuel mixture for optimal performance and fuel efficiency. The heater element in the sensor helps it reach the operating temperature more quickly for accurate readings.

When the ECM detects a high resistance in the heater circuit of the Bank 1, Sensor 3 oxygen sensor, it triggers the P0055 fault code. This could be caused by various factors such as a faulty sensor, damaged wiring, or a problem with the ECM itself.

To diagnose and fix this issue, you can follow these steps:

  1. Inspect the wiring and connectors: Check for any signs of damage, corrosion, or loose connections in the wiring harness, especially around the sensor and the ECM. Repair or replace any damaged components as necessary.

  2. Test the oxygen sensor: Use a multimeter to measure the resistance of the sensor's heater circuit. Compare the readings against the manufacturer's specifications. If the resistance is outside the acceptable range, you may need to replace the oxygen sensor.

  3. Check the fuse: Some vehicles have a dedicated fuse for the oxygen sensor heaters. Make sure the fuse is intact and functioning properly. Replace a blown fuse if necessary.

  4. Consult a professional: If you're unable to diagnose or fix the issue on your own, it is recommended to seek assistance from a qualified mechanic or dealership. They have the necessary tools and expertise to accurately diagnose and repair the problem.

In conclusion, the P0055 fault code indicates a problem with the heater resistance in the Bank 1, Sensor 3 oxygen sensor. It is important to address this issue as it can affect the accuracy of the oxygen sensor readings and overall engine performance.


What are the symptoms of the P0055 code?

The P0055 fault code indicates a problem with the HO2S (Heated Oxygen Sensor) heater circuit in Bank 1, Sensor 3. Here are some symptoms that may be associated with this fault code:

  • Check Engine Light (CEL) illuminated
  • Reduced fuel economy
  • Rough idling or stalling
  • Poor engine performance
  • Black smoke from the exhaust
  • Failed emission test

If you experience any of these symptoms, it is recommended to have your vehicle diagnosed and repaired by a qualified mechanic.


What causes the P0055 code?

The P0055 fault code refers to a problem with the HO2S (Heated Oxygen Sensor) heater resistance in Bank 1, Sensor 3. This code indicates that the electrical circuit resistance in the heater of the third oxygen sensor in Bank 1 is outside of the expected range.

There can be several causes for this fault code, including:

  1. Faulty sensor: The HO2S sensor itself may be defective and not functioning properly.

  2. Wiring issues: Damaged or malfunctioning wiring can cause resistance problems in the heater circuit of the sensor.

  3. Poor electrical connection: Loose or corroded electrical connections can disrupt the operation of the sensor heater.

  4. Faulty ECM (Engine Control Module): In rare cases, a malfunctioning ECM can send incorrect signals to the sensor, causing the fault code to appear.

To diagnose and fix the P0055 fault code, you should start by inspecting the wiring and electrical connections leading to the Bank 1, Sensor 3 oxygen sensor. Look for any signs of damage, such as frayed wires, loose connections, or corrosion. If any issues are found, they should be repaired or replaced as necessary.

If the wiring and connections are in good condition, the oxygen sensor itself may need to be tested. Using an appropriate diagnostic tool, check the resistance of the sensor heater circuit. Compare the measured resistance to the specifications provided by the vehicle manufacturer. If the resistance is outside of the expected range, the oxygen sensor should be replaced.

If the fault code persists after repairing or replacing the sensor, further diagnosis may be required to check the ECM and other related components.

It is recommended to consult a qualified mechanic or utilize professional diagnostic equipment to accurately diagnose and resolve the P0055 fault code.

Possible Solutions

How to fix P0055?

To fix the P0055 fault code on cars, which indicates a HO2S (Heated Oxygen Sensor) Heater Resistance issue for Bank 1 Sensor 3, follow these steps:

  1. Check the wiring: Inspect the wiring harness that connects to the sensor for any visible damage, such as frayed or broken wires. Repair or replace any damaged wiring as necessary.

  2. Check the connector: Ensure that the connector for the sensor is securely connected and free of any corrosion or dirt. Clean or replace the connector if needed.

  3. Test the sensor: Use a multimeter to test the resistance of the sensor heater. The specific resistance values vary by manufacturer and model, so refer to the vehicle's service manual for the correct specifications. If the sensor fails the resistance test, it may need to be replaced.

  4. Check the fuse: Locate and inspect the fuse related to the HO2S Heater circuit. If the fuse is blown, replace it with a new one of the same rating. If the fuse repeatedly blows, there may be an underlying electrical issue that needs to be addressed.

  5. Check the relay: In some cases, the fault may be caused by a faulty relay that controls the sensor heater circuit. Test the relay using a multimeter or replace it if necessary.

  6. Clear the fault codes: After performing the necessary repairs, use an OBD-II scanner or a code reader to clear the fault codes from the vehicle's memory. This will reset the system and allow you to see if the issue has been resolved.

If you are not comfortable performing these steps yourself, it is recommended to take your car to a qualified mechanic or dealership for diagnosis and repair.