P261F: Coolant pump reports substantial speed when it should be off

P261F detects an off-command coolant-pump speed that still resembles running operation in the reviewed GM monitor. It compares commanded state with reported actual speed, so the evidence is a mismatch rather than a direct measurement of coolant flow.

The feedback threshold is high enough to represent operation

The documented failure boundary is feedback speed at or above 3,300 rpm. The enable logic includes an off-state command-speed range of 0–299 rpm and a three-second qualification. Failure must occupy 16 seconds of a 20-second window.

These conditions distinguish a brief rundown from persistent high-speed feedback. A momentary nonzero speed immediately after a command change is not the same as meeting this sustained criterion.

Supply and feedback validity matter

The 12-volt system must be above 11 V to enable the monitor, with disabling hysteresis below 10 V. Listed actual-speed feedback fault states must be inactive. Thus a speed value obtained with invalid feedback or insufficient supply cannot simply be compared against the normal decision rule.

Preserve requested speed, reported speed and supply status together. The monitor can show that the reported operating state is wrong for the command; it does not by itself distinguish unintended pump operation from every possible feedback fault.

Verification should establish an appropriate off-state speed response over the full evaluation window using the vehicle's cooling-system procedure. The code does not directly prove overheating, coolant loss or an obstruction. The source lists Type B, two-trip behavior without specifying a mandatory pump replacement.

Source and applicability

These limits describe the stated monitor and require vehicle, hardware and calibration confirmation. GM diagnostic table, PDF page 662.