What Does P0055 Mean?
The PCM has detected that the heater resistance of the Bank 1, Sensor 3 heated oxygen sensor is outside the expected range. Sensor 3 is typically located downstream of a secondary catalytic converter on vehicles with extended exhaust monitoring. The PCM measures heater current draw and voltage to calculate resistance, and the result is out of the manufacturer's calibrated window. The driver will see a check engine light but is unlikely to notice any performance change.
Common Causes
40%
Aging O2 sensor with heater resistance drifted outside specification
25%
Corroded or high-resistance connections at the sensor connector
20%
Wrong part number O2 sensor installed in the Sensor 3 position
15%
PCM heater monitoring circuit calibration or ground issue
Diagnostic Steps
1
Disconnect the Bank 1 Sensor 3 O2 sensor and measure heater resistance — compare to the manufacturer's specification. Note that Sensor 3 may have a different specification than Sensors 1 or 2.
2
Verify the correct part number sensor is installed for this position and vehicle application.
3
Inspect the sensor connector for corrosion, spread terminals, or heat damage. This sensor's connector is typically located further from the engine and may be exposed to road spray and debris.
4
Perform a voltage drop test across the heater circuit connections while active — any single connection showing more than 0.1V drop should be cleaned or repaired.
5
If the sensor tests within spec on the bench, verify PCM grounds and check for any TSBs (Technical Service Bulletins) related to false heater resistance codes on your specific vehicle.
Estimated Repair Cost
$80 - $300
Parts + labor, varies by vehicle and location
The PCM has detected that the heater resistance of the Bank 1, Sensor 3 heated oxygen sensor is outside the expected range. Sensor 3 is typically located downstream of a secondary catalytic converter on vehicles with extended exhaust monitoring. The PCM measures heater current draw and voltage to ca...
The most common cause of P0055 (HO2S Heater Resistance Bank 1 Sensor 3 (PCM)) is: Aging O2 sensor with heater resistance drifted outside specification
Typical repair costs for P0055 range from $80 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive with no performance impact. Sensor 3 is strictly a monitoring sensor. This code is primarily an emissions compliance concern. Repair at your convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0055 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions / Exhaust
Difficulty
Type
Generic (SAE)
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