Powertrain, generic (extended)

P227A Barometric Pressure Sensor C Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P227A is the general circuit fault of barometric pressure sensor C, used when the control unit finds the signal missing or unusable without classifying it as too low or too high. Sensor C is not necessarily a separate ambient sensor: in GM's 2018 diesel tables the BARO C channel belongs to the turbocharger inlet pressure sensor, GM also uses it on the supercharged 6.2 L LT4, and on its 2023-2024 twin-throttle engine it reads pressure ahead of a throttle. No manufacturer documents P227A itself publicly; GM divides circuit monitoring of sensor C into P227C (low), P227D (high) and P227E (erratic). The matching general codes for sensors A and B are P2226 and P222A. With a substitute value the engine keeps running, but altitude and boost corrections lose accuracy.

Likely causes

Loose connector, corroded pins or damaged wiring at sensor C
Sensor C itself failed
5 V reference or sensor ground shared with other sensors disturbed

Symptoms

  • MIL on
  • Usually no noticeable change in driving; slight power loss at altitude possible

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–350
Time0.5–2 h

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

Parts involved

barometric pressure sensorsensor wiring

Related codes

P227BP227CP227DP227EP2226P222A

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.