P25B4: Wastegate A stuck-closed is a timed control disagreement

P25B4 is the closed-side jam classification for the bank-one wastegate in the cited GM strategy. The controller first needs a persistent control deviation beyond the listed ±40% band. A position boundary then classifies the direction of the failure; the code is not based on one universal opening percentage.

Read the two position cases

When the status saying zero-percent means closed is false, the table uses position above 50% for this classification. When that status is true, it uses position below 50%. The status determines how a numerical position should be interpreted, so recording percentage without its convention can be misleading.

Eligibility limits a repeat test

The source requires the actuator to be active and excludes initial end-stop learning, active actuator testing and a disabled power stage. It also excludes a frozen-actuator cold-start condition. The control-deviation timing exceeds one second, rather than treating every transient mismatch as a jam.

For verification, establish whether the same controller conditions were met and whether the error persisted on the closed side of the configured travel. The summary supports that classification but does not identify a replacement part, actuator adjustment or mechanical repair procedure.

Document scope and source

2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.

GM physical PDF page 863, GM physical PDF page 864, GM physical PDF page 865.