P215A: Wheel-speed information fails the brake controller’s correlation checks

P215A appears in the brake-control section of the reviewed GM document as vehicle-speed versus wheel-speed correlation. The main code row contains checks for simultaneously suspicious sensor information and for identifying an invalid wheel-speed signal.

Keep the correct row in view

The same PDF page contains several wheel-speed plausibility tests above P215A. Those preceding rows must not automatically be assigned to this code. The P215A row itself first counts more than two simultaneous sensor-signal monitoring suspicions, with ignition on and a half-second criterion.

A second listed strategy compares the maximum and minimum wheel speeds while vehicle speed exceeds 3.1 mph. The document gives a large 52.12-mph difference threshold and a 9-to-72-second decision interval. These values belong to this particular brake-controller strategy, not a general tolerance for wheel-speed mismatch.

Diagnostic interpretation

Multiple suspect inputs are a different problem from one consistently offset sensor. Preserve all available wheel-speed channels and the brake controller's accompanying fault information so that the pattern remains visible. Looking at just a calculated vehicle-speed value can conceal the disagreement being assessed.

The monitor is listed as continuous and Type B, two trips. However, ignition on alone does not satisfy the moving-vehicle condition of the second check. A stationary check cannot establish its successful completion.

Because this evidence concerns information used by brake control, verification belongs in an appropriate professional diagnostic setting. The code does not identify a particular wheel, prove a brake's mechanical condition or establish that continued driving is safe.

Source and applicability

The thresholds and component mapping apply only to the documented monitor, pending vehicle and calibration confirmation. GM diagnostic table, PDF page 65.