P2796: Auxiliary transmission-pump motor circuit is diagnosed open

P2796 checks the auxiliary transmission-fluid pump motor and wiring for an open electrical path in the reviewed GM strategy. It does not directly measure hydraulic pressure or establish that the pump is mechanically unable to move fluid.

The fault is derived from circuit voltage

The controller compares voltage with its accepted range. Its design specification for an open path is impedance above 200 kilohms between signal and controller ground. The stated counting thresholds exceed 20 failed counts and 25 sample counts, with a 100-millisecond update rate.

Those are controller detection criteria, not instructions to measure resistance on an operating pump circuit. A short-lived abnormal reading also needs to be considered against the full sample window.

Pump supply architecture matters

Battery voltage must be above 9 V and below 15 V, and run/crank voltage must exceed 5 V for more than 25 milliseconds. Both diagnostic monitoring and reporting must be enabled.

The table accommodates pumps supplied through a high-side driver and pumps not supplied through one. The selected path must be understood before assuming that an absent high-side-driver command is itself abnormal. Confirm the actual circuit architecture using vehicle-specific information.

Verification should establish an intact motor-control path and a completed enabled diagnostic without recurrence. If a separate pressure-performance complaint exists, keep that hydraulic evidence distinct from this open-circuit finding. The source documents Type B, two-trip behavior and does not identify a failed connector or mandate replacing the pump.

Source and applicability

Keep the stated transmission function and source calibration separate from other applications. GM diagnostic table, PDF page 1194.