P27AD: pressure-control solenoid G characterization data is invalid

P27AD is a calibration-data diagnosis for pressure-control solenoid G. The controller checks stored characterization information against the installed valve-body component type. The source's mappings include different clutch, line-pressure and CVT mode-valve functions, so the letter G is not a universal physical-location label.

Four ways the data check can fail

The programming-complete flag can remain false because data is missing or incomplete, the solenoid class conflicts with controller calibration, the checksum is inconsistent, or the characterization axis is invalid. The continuation explains that successive axis values must not decrease. These are stored-data checks, not direct hydraulic-pressure tests.

The monitor executes once at normal controller power-up, during initialization before the normal control loop. Reporting is Type A, one trip. The source says factory and service characterization should correspond to the installed valve-body assembly identity.

Useful next evidence

Review hardware identity, programming completion and the specific data-integrity result before blaming hydraulic performance. A solenoid can be electrically connected while its stored characterization remains wrong. Conversely, reprogramming with data from a different assembly would not satisfy the intended hardware match.

Use the authorized service programming process and verify the initialization result on the next qualifying power-up. A successful road shift alone does not establish that the data-integrity monitor passed, and this table does not justify replacing a solenoid solely from P27AD.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 2276. GM diagnostic parameters, PDF page 2277.