P227B: the documented BARO C code tests turbo-inlet pressure agreement

The dictionary calls P227B barometric-pressure sensor C range/performance. The reviewed GM row instead names turbocharger-inlet air pressure, or TCIAP, in a three-pressure-sensor configuration. That source-specific role must be established before selecting a sensor from the generic label.

Outlier logic identifies the TCIAP channel

TCIAP must disagree with both BARO and manifold absolute pressure while BARO and manifold pressure agree with each other. The running comparison uses an airflow-dependent threshold, ranging in the supporting table from 10 to 43 kPa across its listed flow points. It is not a universal fixed pressure tolerance.

When the engine is not rotating, the continuation uses a 10-kPa agreement boundary and also checks TCIAP against 50–115 kPa limits. That branch requires the stated more-than-five-second interval and absence of listed active or pending circuit faults.

Verification needs the operating branch

Running eligibility includes speed below 985 rpm, fuel request below 25 mm³, throttle above 90%, coolant above 60°C and relay voltage above 11 volts. The running counter uses 240 failures in 300 samples; the stopped branch uses four in five, with 12.5-millisecond sampling. Reporting is Type B over two trips.

A useful verification captures all three pressures and confirms which comparison completed. A plausible isolated TCIAP number cannot establish agreement. The source supplies no physical sensor location or replacement verdict. Its terminology and limits apply only to this documented 2025 GM arrangement pending vehicle-specific confirmation.

Source: GM monitor, PDF page 801; GM monitor, PDF page 802; GM monitor, PDF page 1627.