P22B1: O2 Sensor Reference Voltage Circuit High (Bank 1 Sensor 2)

P22B1 is set when the reference voltage (Nernst-cell) line of the bank 1 downstream wide-band probe reads above its valid range. Because the cell delivers only a few hundred millivolts across about 300 ohms, any contact with the heater feed or another live wire overrides it. A cracked ceramic letting the heater circuit leak into the cell can do the same. No maker publishes this code with a threshold; for the upstream sensor, Ford and Saab already treat a voltage above 4.7 V as an open reference line, while Ford sends shorts to power to P0132. CARB demands detection of out-of-range values on air-fuel sensors behind the aftertreatment. P22AE covers the open, P22B0 the low reading, P22BE bank 2 and P2246 the upstream twin.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank. Sensor 2 is the sensor after the catalytic converter.

Symptoms

• Check engine light
• Downstream oxygen reading stuck at a limit

Most likely causes

• Nernst-cell wire shorted to the heater supply or another live wire
• Cracked sensor ceramic leaking heater voltage into the cell
• Faulty sensor interface in the ECM or sensor module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P22B1 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• B1: Specific fault in that system

Frequently asked questions

Can I keep driving with code P22B1?

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 P22B1?

The most common causes are: nernst-cell wire shorted to the heater supply or another live wire; cracked sensor ceramic leaking heater voltage into the cell; faulty sensor interface in the ECM or sensor module.

Related codes

• P22AEO2 Sensor Reference Voltage Circuit/Open (Bank 1 Sensor 2)
• P22AFO2 Sensor Reference Voltage Performance (Bank 1 Sensor 2)
• P22B0O2 Sensor Reference Voltage Circuit Low (Bank 1 Sensor 2)
• P22BEO2 Sensor Reference Voltage Circuit High (Bank 2 Sensor 2)
• P2246O2 Sensor Reference Voltage Circuit High (Bank 1 Sensor 1)

Sources

• law.cornell.edu: 13 CCR 1968.2
• bosch-motorsport.com: Data Sheet 69034379 Lambda Sensor LSU 4.9
• newtonnet.co.uk: fordobd2012
• saabwisonline.com: dtc p2237 p2239 p2243 p2251 or p2626

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.