Powertrain, generic (extended)

P2C63 O2 Sensor Pumping Current Trim Circuit Low Bank 1 Sensor 3

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2C63 reports that the oxygen value from the third exhaust sensor of bank 1 has dropped below its physically possible minimum. Despite the trim wording, GM uses it on the 3.0L Duramax diesel for the O2 signal of NOx sensor 3, which sits behind the second catalyst: table 25OBDG04B (2025) fails a reading under -6 percent in 100 of 200 samples on a 25 ms task, with the engine running, supply above 11 V and the sensor ready; Type B, MIL after two trips. GM's PIT5751C and bulletin 21-NA-149 name P2C63 among many codes on 2020-21 Silverado, Sierra, Tahoe, Yukon and Escalade with the 3.0L LM2; the cause was an engine harness rubbed through above the generator or shorted against the clamp of the crankcase-pressure-regulator hose. P2C64 is the high side, P23AE the NOx circuit low code of this sensor.

Likely causes

Engine harness chafed or shorted (GM 3.0L LM2 - at the generator or the crankcase pressure regulator clamp)
Third exhaust sensor (on GM diesels NOx sensor 3) reporting an implausibly low O2 value
Corroded or loose sensor connector

Symptoms

  • MIL on after two trips
  • On the GM LM2 often many other codes, rough running or blown fuses when the harness is damaged
  • Aftertreatment monitors not completing

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 b1s3nox sensoroxygen sensor wiringecm

Related codes

P2C62P2C64P2C65P23AEP2627

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