P227D: BARO sensor C reports pressure above its calibrated ceiling

P227D identifies an excessive BARO C pressure value in the reviewed GM implementation. Its generic circuit-high wording must be read alongside the actual architecture: the MAF sensor communicates the pressure value to the ECM digitally over LIN.

The monitored quantity is absolute pressure

The diagnostic fails for BARO C above 110 kPa after communication with the MAF sensor has been established. It does not publish an external signal-wire voltage threshold. A generic analog pressure-sensor test therefore cannot be assumed to reproduce this monitor.

The C channel also needs to be distinguished from other pressure parameters. A plausible manifold-pressure display or another BARO channel does not demonstrate that this particular value is correct.

Evaluate persistence and reporting together

Sampling occurs every 25 milliseconds, with 160 failing samples required out of 200. Record whether the high value persists through that window and whether it is received through an otherwise functioning data path.

An independent ambient-pressure comparison is useful only if the units and absolute-pressure convention match. A disagreement then supports further investigation of the sensing/reporting system; it does not, by itself, identify which electronics or circuit element is responsible.

Repair verification should confirm plausible BARO C values and a completed enabled test without recurrence. The table lists Type A, one-trip behavior. Exact vehicle applicability, component position and connector information remain outside this source, so the monitor description should not be treated as a parts-selection guide.

Source and applicability

Use these facts only after confirming the documented system and calibration for the vehicle. GM diagnostic table, PDF page 634.