P26E7: Supply D open-load may be discovered only when shutting down

P26E7 is the actuator-supply-D open-load code mapped to high-side output eight in this GM transmission table. The test is deliberately performed at powerdown. A disabled HSO8 should be pulled down through a load when the corresponding low-side output is enabled.

The retained result explains timing

If HSO8 stays above 40% of battery voltage, the controller records an open-load result. It later reads that nonvolatile record and sets the code during startup. The code’s appearance therefore does not pinpoint when the underlying condition was measured.

The continuation page supplies a 60 ms failure interval, supply eligibility and a battery-change limit below 1.5 V. P0882 or P0883 disables the check. Reading only the first page would omit these important test conditions.

What counts as verification

Confirm that a later shutdown actually executed the HSO8 test with eligible voltage, then inspect its result. A normal value during an ordinary powered state cannot substitute for that evidence. The generic supply letter must be mapped to the actual controller circuits before component testing. This monitor classifies an ineffective load path; it does not prove that one particular actuator or wire is open.

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 937, GM physical PDF page 938.