P0155: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
Can you still drive? Yes, the vehicle is safe to drive. The only effect is delayed closed-loop fuel control after cold starts, which increases emissions and slightly reduces fuel economy during warm-up.
What Does P0155 Mean?
Code P0155 indicates a problem with the heater element inside the Bank 2 upstream oxygen sensor. The heater brings the sensor up to operating temperature quickly after engine start. Without a functioning heater, the sensor takes much longer to begin working, resulting in extended open-loop operation and higher cold-start emissions.
Need to read your codes?
An OBD-II scanner lets you read and clear diagnostic trouble codes from your vehicle's computer. Most scanners work with any car made after 1996.
Browse OBD-II Scanners on AmazonCommon Causes
- Burned-out O2 sensor heater element
- Blown O2 sensor heater fuse
- Damaged wiring to heater circuit
- Corroded heater circuit connector
Symptoms
- Check engine light on
- Poor fuel economy during warm-up
- Failed emissions test
- Extended time before closed-loop operation
Diagnostic Steps
- 1Read and document freeze frame data
- 2Check the O2 sensor heater fuse
- 3Measure heater circuit resistance at the sensor connector
- 4Verify battery voltage reaches the heater circuit
- 5Inspect wiring for damage between fuse box and sensor
- 6Replace O2 sensor if heater resistance is out of specification
Recommended Parts & Tools
oxygen sensor
automotive fuse kit
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $50 - $350 |
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Frequently Asked Questions
Why do O2 sensors have heaters?
O2 sensors must reach approximately 600 degrees Fahrenheit to function properly. The built-in heater brings the sensor to operating temperature within 30-60 seconds of engine start rather than waiting minutes for exhaust heat alone.
Should I check the fuse before replacing the sensor?
Absolutely. A blown heater fuse is a quick, inexpensive fix. Always check the fuse first before spending money on a new O2 sensor.
Community Fix Reports
Community reports are user-submitted and not verified by Auto AI Buddy. Results may vary.
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