Powertrain, generic (extended)

P22B7 O2 Sensor Pumping Current Trim Circuit High (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P22B7 is, going by its title, the high fault on the trim circuit belonging to bank 1's downstream wide-band probe. In GM's diesel tables (2016, 2018 and 2025 group 04) the code is a ceiling test on the oxygen value of the second NOx sensor: the 2016 table flags readings above 24 %, which is more oxygen than fresh air holds, in 100 of 200 samples. The test runs only while exhaust back-pressure stays below its limit, no exhaust brake is active and no NOx sensor pressure fault is pending; GM rates it Type B, two trips. GM bulletin 21-NA-149 lists it for the 3.0 Duramax LM2 alongside harness chafing. No public source gives a trim-resistor threshold. P22B5 is the open, P22B6 the low case, P22C4 bank 2. The lamp lights.

Likely causes

Faulty downstream NOx/oxygen sensor reporting excess oxygen
Chafed engine harness affecting the sensor lines (GM 3.0 LM2)
Trim or signal wire shorted to a voltage source

Symptoms

  • Check engine light
  • Downstream oxygen value above 21 % in live data

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

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

Parts involved

oxygen sensor bank1 sensor2nox sensoroxygen sensor wiringecm

Related codes

P22B5P22B6P22C4P2628

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.