P2230: Barometric pressure fluctuates too much over consecutive samples

P2230 identifies excessive noise in the LIN-reported barometric-pressure signal in this GM monitor. It is a variability check: a pressure value can remain within broad high and low limits yet change too erratically to be credible.

How the controller measures noise

Every 25 milliseconds, the controller calculates the absolute change from the previous BARO reading. It sums these changes across 40 consecutive readings. The source calls that accumulated movement a string length.

The threshold is string length greater than 100 kPa, not an atmospheric-pressure reading greater than 100 kPa. Repeated up-and-down movement adds to this quantity even when the signal finishes near its starting value. Confusing the accumulated variation with pressure itself would fundamentally misread the monitor.

What a useful recording includes

Each evaluated sample takes one second, and four failures out of five establish the fault. The diagnostic also requires established LIN communication with the MAF sensor. A slow scan display may hide the rapid oscillation used in that calculation, while a communications interruption needs its own interpretation.

Capture the reported pressure with enough temporal detail to assess instability, using appropriate service equipment and the vehicle's specified procedure. Compare behavior over a complete evaluation window instead of relying on a plausible single reading.

The source documents Type A, one-trip behavior. Successful verification means stable pressure reporting and a completed noise diagnostic without recurrence; the table does not identify an individual defective wire or require sensor replacement.

Source and applicability

The documented system and calibration must be confirmed for the vehicle before using these limits. GM diagnostic table, PDF page 618.