P0055 — HO2S Heater Resistance (Bank 1, Sensor 3) | OBD-II Code

What Does This Error Mean?

Code P0055 means the heater resistance in the Bank 1, Sensor 3 oxygen sensor is outside the acceptable range. Sensor 3 is a third oxygen sensor — found on some vehicles with two catalytic converters or specialized emission systems. Not all vehicles have a Sensor 3, so P0055 is less common than P0053 or P0054.

Affected Models

Some V6 and V8 trucks and SUVs
Ford F-250 Super Duty
Chevrolet Suburban
Toyota Land Cruiser
Lexus LX series

Common Causes

The Sensor 3 oxygen sensor heater element has failed or drifted out of resistance spec
Corrosion or moisture inside the wiring connector affecting the resistance reading
Heat damage from being positioned close to a second catalytic converter
An incorrect replacement sensor was installed with the wrong resistance
Wiring damage in the harness between the sensor and ECM

How to Fix It

Verify your vehicle actually has a Bank 1, Sensor 3. Check your owner's manual or a vehicle-specific repair guide to confirm the exhaust layout.

If your vehicle does not have a third sensor, the code may point to a wiring fault or an ECM data error.
Scan for all stored codes and note any related oxygen sensor or catalytic converter codes at the same time.

Multiple sensor codes together suggest a wiring harness issue rather than individual sensor failures.
Locate Sensor 3 on the exhaust system — usually after the second catalytic converter. Inspect the wiring harness and connector carefully.

The third sensor is often in a tight space near the rear of the vehicle.
Unplug the sensor and test heater resistance with a multimeter. If out of spec, replace the sensor with the exact correct part.

Third-position sensors are less common, so verify the part number carefully before ordering.
Reinstall, clear the code, and run a full drive cycle. Rescan after driving to confirm the code does not return.

Allow the engine to cold-start and complete a full warm-up including highway driving.

When to Call a Professional

P0055 is less common and the sensor location can be hard to reach on some vehicles. If you cannot locate Sensor 3 or the wiring is complex, a shop with a factory service manual is the safest option. Expect $175–$375 for diagnosis and sensor replacement.

Frequently Asked Questions

Why does my car have three oxygen sensors on one bank?

Some larger vehicles with two catalytic converters per exhaust bank use three oxygen sensors. One before the first converter, one between the converters, and one after the second converter. This allows the ECM to monitor the efficiency of each converter individually.

Is P0055 a serious problem?

It is worth fixing but not an emergency. The heater circuit fault means Sensor 3 may not warm up as quickly as needed. This primarily affects emissions monitoring accuracy. Fix it within a few weeks to avoid failing an emissions test.

Can I drive with P0055?

Yes, in most cases you can drive normally. The engine will not typically enter a safety mode from this code alone. However, your emissions readiness monitors may be incomplete, which will cause an emissions test failure.