O2 Sensor Heater Resistance Issue (Bank 1, Sensor 3)
The P0055 code indicates that the Engine Control Module (ECM) has detected a heater circuit resistance problem in the oxygen sensor located after the catalytic converter on Bank 1 (the side of the engine with cylinder #1). The heater element is essential for the sensor to reach operating temperature quickly, especially during cold starts. A resistance outside the specified range can cause inaccurate readings, affecting fuel trim and emissions.
01. Most Common Causes
- Faulty oxygen sensor (Bank 1, Sensor 3)
- Open or shorted heater circuit wiring
- Blown fuse for the O2 sensor heater circuit
- Corroded or damaged connector
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Rough idle or hesitation
03. 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 O2 sensor wiring and connector for damage, corrosion, or loose connections.
Step 3: Measure the resistance of the heater circuit at the sensor connector (typically 2-10 ohms). Compare to manufacturer specs.
Step 4: Check the heater circuit fuse and relay. If OK, test for voltage at the sensor connector with the ignition on.
Step 5: If voltage and ground are present but resistance is out of spec, replace the oxygen sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause poor fuel economy and increased emissions. Prolonged driving could damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for a DIY sensor replacement, or $150-$300 at a shop including labor.