The OBD2 code P0055 indicates an issue with the “HO2S Heater Resistance Bank 1 Sensor 3,” pointing to a malfunction in the heating element of the oxygen sensor located in Bank 1, Sensor 3 of the exhaust system.
This specific sensor is part of the vehicle’s emissions control system, helping regulate the fuel-to-air ratio by measuring the oxygen content in the exhaust gases. Problems with this sensor can lead to inefficient engine operation, increased emissions, and may trigger the malfunction indicator lamp (MIL).
P0055 quick overview
| Meaning | P0055: HO2S Heater Resistance Bank 1 Sensor 3 |
| Is it serious? | Moderately serious, as it can affect the vehicle’s fuel efficiency and emissions performance. |
| Possible causes | – Faulty or failing oxygen sensor heater – Corroded or damaged wiring and connectors – Issues with the powertrain control module (PCM) or engine control module (ECM) circuitry – Poor electrical connections or ground issues |
| How to diagnose? | Check for proper power and ground at the oxygen sensor connector. Verify continuity of the heater circuit in the wiring harness. Inspect the PCM (Ford) or ECM (Toyota) for any faults related to oxygen sensor heater control. Test for excessive resistance in the heater circuit using a multimeter. Reset related systems like the valvetronic motor (BMW) if misfires or other issues persist. |
P0055 Meaning
When you see a P0055 code, it means there’s a problem with the heater in one of your car’s oxygen sensors, specifically the one called Bank 1 Sensor 3. This heater helps the sensor reach its optimal working temperature faster, which is important for accurately measuring exhaust gases and keeping your engine running efficiently.
If this heater isn’t working right, your car might not run as smoothly, use more fuel, or emit more pollution. Fixing this issue usually involves checking the sensor’s electrical connections, making sure it’s getting power, and sometimes replacing the sensor or fixing wiring problems.
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How to fix P0055 – learn from mechanics
I looked into P0055 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: BMW P0055
Vehicle information 2007 BMW X3 3.0si 3.0L
Issue + repair history
- MIL lamp illuminated
- Cylinder 1 and 3 misfires detected
- Oil found in spark plug tubes, replaced valve cover gasket
- Compression test performed, no issues found
- Replaced spark plugs, coils, and injector for cylinder 1
- Misfire persisted despite component replacements
- Code P0049: Turbo / Supercharger Turbine Overspeed
Other OBD2 Codes + Test Results
- P0301: Cylinder 1 misfire
- P0303: Cylinder 3 misfire
- C342d: Unknown
- P0055: HO2S heater resistance B 1 S 3
Mechanic suggestions
- Check for proper triggering of coils and injectors
- Verify operation of ignition components using diagnostic tools
- Perform a leak down test to assess cylinder integrity
- Smoke test for vacuum leaks in the intake system
- Monitor fuel trims and perform a fuel pressure test
- Check crankcase vacuum and emissions gases for signs of head gasket leaks
- Test compression to ensure mechanical integrity of the engine
Final fix
- Reset valvetronic motor using scanner
- Misfires resolved after resetting valvetronic motor, indicating an issue with valvetronic system
Case #2: Ford P0055
Vehicle information 2010 Ford F-150 5.4L V8 Triton
Issue + repair history
- MIL lamp illuminated with code P0055
- Replaced Bank 1 Sensor 3 (downstream oxygen sensor)
- Checked wiring harness for damage or corrosion
- Code P0055 persisted after sensor replacement
Other OBD2 Codes + Test Results
- P0055: HO2S Heater Resistance Bank 1 Sensor 3
- No other codes reported
- Live data showed stable oxygen sensor voltage during operation
Mechanic suggestions
- Check for proper power and ground at the sensor connector
- Verify continuity of heater circuit in the wiring harness
- Inspect PCM (Powertrain Control Module) for faults related to oxygen sensor heater control
- Test for excessive resistance in the heater circuit using a multimeter
Final fix
- Discovered corroded terminal at the PCM connector for Bank 1 Sensor 3
- Cleaned and repaired terminal, cleared codes, and reset PCM, resolving the issue
Case #3: Toyota P0055
Vehicle information 2012 Toyota Camry 2.5L Inline-4
Issue + repair history
- MIL lamp illuminated with code P0055
- Replaced Bank 1 Sensor 3 (downstream oxygen sensor)
- Inspected wiring harness for damage or corrosion
- Code P0055 persisted after sensor replacement
Other OBD2 Codes + Test Results
- P0055: HO2S Heater Resistance Bank 1 Sensor 3
- No other codes reported
- Live data showed stable oxygen sensor voltage during operation
Mechanic suggestions
- Check for proper power and ground at the sensor connector
- Verify continuity of heater circuit in the wiring harness
- Inspect ECM (Engine Control Module) for faults related to oxygen sensor heater control
- Test for excessive resistance in the heater circuit using a multimeter
Final fix
- Discovered damaged wiring at the oxygen sensor connector
- Repaired wiring, cleared codes, and reset ECM, resolving the issue
How to diagnose P0055
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Explanation |
|---|---|
| Check for proper power and ground | Ensure the oxygen sensor is receiving the correct voltage and has a good ground connection. |
| Verify continuity of the heater circuit | Use a multimeter to check for a continuous electrical path in the sensor’s heater circuit. |
| Inspect the PCM or ECM | Look for any faults in the vehicle’s computer that could affect the oxygen sensor’s heater control. |
| Test for excessive resistance | Measure resistance in the heater circuit to ensure it falls within the manufacturer’s specified range. |
| Reset related systems | For BMW, resetting systems like the valvetronic motor can resolve related misfire issues. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko