Powertrain, generic (extended)

P227B Barometric Pressure Sensor C Circuit Range/Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P227B means sensor C supplies an electrically sound signal that does not agree with the other pressure readings. In GM's 2018 diesel tables sensor C is the turbocharger inlet pressure sensor: the ECM compares it with BARO and MAP at idle and in the window between key-off and the next start, and if only sensor C is out of line it gets the blame, as a Type B fault after 320 failures in 400 samples. With the engine stopped a reading below 50 or above 115 kPa also fails. On GM's 2023-2024 twin-throttle engine the pressure ahead of a throttle is checked against ambient pressure while running and while stopped, with 2 kPa tolerance plus allowances for modelled air-filter loss; the code sets after 2 s within one trip. P227C to P227E cover electrical faults of the same sensor.

Likely causes

Sensor C drifting or with an offset

Sensor port blocked by dirt, oil or ice, or sensor not seated in its bore

Heavily clogged air filter shifting the pressure ahead of the compressor or throttle

Symptoms

MIL on
Mostly no driveability change; occasionally reduced boost

Repair estimate

DifficultyMediumDIY possible

Parts and labour€40–400

Time0.5–2 h

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

Parts involved

barometric pressure sensor

References: gsi.ext.gm.com, gsi.ext.gm.com.