P263A: MIL circuit low is assessed while the lamp driver is off

P263A concerns the malfunction-indicator lamp output circuit being low when the driver is off. In the cited GM diagnostic, that command state makes the low voltage consistent with the controller’s short-to-ground classification. The code describes electrical feedback, not the seriousness of a separate engine fault.

Match voltage to driver command

An off-state low result is not interchangeable with P263B’s on-state high result. The two checks use different commands to distinguish electrical fault modes. A voltage reading without its command state can therefore be misleading.

The P263A row requires run/crank voltage above 11 V and remote vehicle start inactive. Its confirmation is one failed observation out of one sample, with a 50 ms sample interval. These are controller criteria; they are not instructions for applying power or ground to an unknown lamp connector.

Do not use the lamp as its own proof

A lamp that remains dark cannot independently demonstrate a sound circuit when its control path is the subject of the fault. The source also notes that certain controllers may set P0650 alongside P263A. Such a companion record does not necessarily represent an unrelated lamp problem.

A useful investigation preserves command, electrical status and the particular controller’s implementation. The monitor does not establish where a grounded path is located or whether the lamp, wiring or output stage is responsible. Localization requires the correct circuit information.

Source and applicability

2025 GM 25OBDG06A documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG06A, PDF page 553. 25OBDG06A, PDF page 554.