Powertrain, generic (extended)

P22B9 O2 Sensor Positive Current Control Circuit Low (Bank 2 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P22B9 means the positive current control (pump-current) line of the bank 2 downstream wide-band probe reads below its allowed band, most often because the lead has worn through and touches ground. No maker documents this code publicly, so the logic can only be inferred from the bank 1 and upstream relatives: GM lists P22AC for the 3.0 Duramax LM2 without a threshold, Saab treats the upstream P2238 as a Type B fault, and Ford books upstream shorts as P0131. CARB requires out-of-range detection on air-fuel sensors behind the aftertreatment. The fault needs a V or boxer engine with a wide-band probe after each catalyst. P22B8 is the open, P22BA the high variant, P22AC the bank 1 code. A lit warning lamp is usually the only symptom.

Likely causes

Pump-current wire chafed through and shorted to ground
Internal short in the bank 2 downstream sensor
Water in the connector

Symptoms

  • Check engine light
  • Bank 2 downstream oxygen value at an extreme

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 bank2 sensor2oxygen sensor wiringecm

Related codes

P22B8P22BAP22ACP2241

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