P208B: reductant pump speed fails to follow its command

P208B is a reductant pump performance code. The reviewed GM controller compares sensed pump speed with the arbitrated speed command and detects an absolute difference greater than 712 rpm. This is a speed-tracking diagnosis, not a direct low-pressure threshold.

Retry behavior is part of the result

The table describes a 63-second sequence combining stabilization attempts, stopped waiting intervals and blocked-pump confirmation. Two retries are allowed in the stated sequence, with the pump stopped for 15 seconds between retries. Once pressure hold is achieved, the retry rules change and the fault can be counted after three seconds of qualifying behavior.

Those details matter when interpreting a pump that starts and stops during diagnosis. A stopped interval can be part of the controller's retry strategy rather than independent evidence of an open motor circuit. Conversely, a single successful spin does not demonstrate that commanded and sensed speeds agree through the qualified test.

States and inhibitors

The monitor is enabled in listed operating states including priming, buildup, closed-loop control and purge. Pressure-sensor, pump, supply, communication or Run/Crank faults can force the pump off and disable this check. Controller-internal faults are also excluded.

The source lists Type A, one-trip reporting and recovery only in the next driving cycle. Verification should review speed error together with pump state and retry history, then confirm the eligible test result. The row does not identify the mechanical or electrical root cause. Exact system applicability and service testing remain vehicle-specific.

Source: GM monitor, PDF page 193.