P22BC concerns the plausibility of the Nernst-cell signal of the wide-band probe fitted after the bank 2 catalyst. The leads test fine, yet the cell voltage that the controller uses as its set point drifts, reacts slowly or cannot be held, so the computed oxygen value loses credibility. No maker documents this code publicly, and none publishes a limit for its upstream relative P2248 either. The usual reasons are physical: an aged cell whose resistance has climbed well above the nominal 300 ohms of a Bosch LSU 4.9, deposits from oil or coolant, or a weak heater. CARB requires a downstream sensor to remain good enough to judge the catalyst. Siblings: P22BB open, P22BD/P22BE low/high, P22AF bank 1. The lamp lights and catalyst results may be withheld.
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
- Bank 2 downstream oxygen reading lags behind or is offset from the other sensors
- Catalyst monitor for bank 2 does not complete
Most likely causes
- Aged downstream wide-band sensor on bank 2 with raised Nernst-cell resistance
- Oil, coolant or additive deposits on the sensing element
- Heater output too low to keep the cell at working temperature
- Contact resistance in the Nernst-cell terminal
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 P22BC means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 2: Fuel injection
- BC: Specific fault in that system
Frequently asked questions
Can I keep driving with code P22BC?
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 P22BC?
The most common causes are: aged downstream wide-band sensor on bank 2 with raised Nernst-cell resistance; oil, coolant or additive deposits on the sensing element; heater output too low to keep the cell at working temperature.
Related codes
- P22BBO2 Sensor Reference Voltage Circuit/Open (Bank 2 Sensor 2)
- P22BDO2 Sensor Reference Voltage Circuit Low (Bank 2 Sensor 2)
- P22BEO2 Sensor Reference Voltage Circuit High (Bank 2 Sensor 2)
- P22AFO2 Sensor Reference Voltage Performance (Bank 1 Sensor 2)
- P2248O2 Sensor Reference Voltage Performance (Bank 2 Sensor 1)
Sources
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.