The heated oxygen sensor on bank 2 is the downstream sensor 2 behind the (first) catalytic converter, used mainly to monitor the converter. Its heating element brings it quickly to operating temperature. Typically the heater receives battery voltage via a fuse, and the engine control module switches the ground side with a pulsed signal while checking that the circuit state matches the command. P0056 is the general circuit fault: the measured state of the heater circuit does not fit the command, most often because the circuit is interrupted. Which physical fault sets the general, low or high code is defined by each manufacturer. Without heating, the sensor becomes ready late and catalyst monitoring may not complete. Bank 2 codes occur only on engines with two exhaust banks (V or boxer engines).
Medium severity. Can I keep driving?Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.
Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines. Sensor 2 is the sensor after the catalytic converter.
Symptoms
- Check engine light on
- Usually no noticeable drivability problem
- Catalyst monitor does not complete
- Emissions test or readiness check failed
Most likely causes
- Heating element inside the sensor burnt out
- Wire or connector damaged by heat or road spray
- Heater fuse blown; a shared fuse can set several heater codes
- Output driver or software of the engine control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0056 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 0: Subsystem depends on the code range
- 56: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0056?
Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.
What causes code P0056?
The most common causes are: heating element inside the sensor burnt out; wire or connector damaged by heat or road spray; heater fuse blown; a shared fuse can set several heater codes.
Related codes
- P0057HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
- P0058HO2S Heater Control Circuit High (Bank 2 Sensor 2)
- P0036HO2S Heater Control Circuit (Bank 1 Sensor 2)
- P0060HO2S Heater Resistance Bank 2 Sensor 2
- P0161O2 Sensor Heater Circuit Bank 2 Sensor 2
Sources
- law.cornell.edu: 13 CCR 1968.2
- saabwisonline.com: dtc p0030 p0036 p0050 p0053 p0054 p0056 p0059 p006
- static.nhtsa.gov: MC 10080421 7690
- en.wikipedia.org: Oxygen sensor
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.