P2C11: Reductant pump current depends on heating or pumping mode

P2C11 is a reductant-pump undercurrent diagnosis, but the expected current depends on what the pump is doing. The cited DEFC controller can use the pump as a heater to assist defrosting, or run its motor to supply fluid. Treating every current reading as a pumping measurement would miss that distinction.

Two operating limits

The source lists a current below 0.75 A when the pump is in heating mode. For priming or running, the listed limit is below 0.5 A. The qualification is four seconds using a 0.01-second sampling time base. The table also requires an active power mode and no active pump hardware protection.

Pump-state, pressure and related-fault conditions further determine eligibility. Some pressure-sensor, pump, supply or communication faults can cause the pump to be switched off, which disables this check. A commanded-off pump is therefore not a meaningful undercurrent test merely because its measured current is small.

Preserve the state with the measurement

Record pump mode, requested operation, current and relevant pressure or protection status together. If an earlier fault shut the pump down, diagnose the reason for shutdown before interpreting its lack of current as fresh proof of a failed motor.

The source says recovery occurs only on the next driving cycle. Immediate disappearance of a current anomaly is therefore not necessarily the same as monitor recovery. Use the exact reductant-system service routine for electrical tests; the mode-specific limits are monitor criteria, not instructions to energize the pump externally or bypass protection.

Source and applicability

2025 GM 04B documented monitor only; module and calibration applicability must be matched to the vehicle. GM PDF, page 208.