O2 Sensor Heater Resistance High (Bank 1, Sensor 3)
The P0055 code indicates that the powertrain control module (PCM) has detected a high resistance in the heater circuit of the oxygen sensor located after the catalytic converter on bank 1 (the side of the engine containing cylinder 1). This sensor is responsible for monitoring catalytic converter efficiency. The heater element helps the sensor reach operating temperature quickly. High resistance can be caused by a faulty sensor, damaged wiring, or poor electrical connections, leading to inaccurate readings and potential emissions issues.
1. Most Common Causes
- Faulty oxygen sensor (Bank 1, Sensor 3)
- Damaged or corroded wiring/connector in the heater circuit
- Blown fuse for the oxygen sensor heater circuit
- PCM failure (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Possible rough idle or hesitation
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the wiring and connector for Bank 1 Sensor 3 for damage, corrosion, or loose connections.
Step 3: Measure the resistance of the heater circuit at the sensor connector (should be between 2-10 ohms). If out of range, replace the sensor.
Step 4: Check the heater circuit fuse and relay; replace if blown.
Step 5: If wiring and sensor are good, test the PCM output for the heater circuit; if no voltage, suspect PCM issue.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause increased emissions and reduced fuel economy. It is safe for short trips, but should be repaired soon to avoid failing an emissions test.
How much does it cost to fix?▼
Typically $150-$300, including parts (oxygen sensor) and labor. DIY replacement can cost around $50-$100 for the sensor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.