P208C: Separating a DEF pump ground-short report from a pressure fault

P208C concerns a low-voltage electrical failure in one of the reductant pump's three motor control phases. In the cited GM table, the specific off-line driver status identifies a short to ground. The code is not generated simply because delivered DEF pressure is low.

Why the pump changes state

While the motor runs, absence of the expected back-EMF event at 60-degree intervals provides an initial fault indication. That running observation does not identify the precise failure mode. The controller therefore switches the pump off so that the driver can distinguish a low-circuit fault from other electrical conditions.

A stopped pump following the initial failure can consequently be part of the intended diagnostic sequence. Treating the stopped state as a separate mechanical seizure would overlook the controller's reason for commanding it off.

Evidence for a useful follow-up

The row requires active vehicle power mode, excludes specified internal controller failures and uses a 0.4-second confirmation period. It describes recovery on a subsequent driving cycle. Retest interpretation must account for that timing and state sequence.

The useful distinction is between a missing running feedback event and the subsequent off-line short-to-ground classification. Preserve both, along with any accompanying circuit faults. The source supports investigating the motor's electrical control path but does not identify a particular damaged wire or mandate pump replacement. Locating the short requires the actual vehicle circuit information and appropriate controlled testing, rather than assumptions based on low pressure alone.

Source and scope

2025 GM 25OBDG04B DEFC monitor calibration only; this document does not establish applicability to every model, engine or reductant system. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 193.