Powertrain, generic (extended)

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

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–450
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

oxygen sensor bank1 sensor2oxygen sensor wiringecm

Related codes

P22AEP22AFP22B0P22BEP2246

References: law.cornell.edu, bosch-motorsport.com, newtonnet.co.uk, saabwisonline.com.