P0CEC: Electronics coolant-pump control reads high

P0CEC identifies hybrid/EV electronics coolant pump A control circuit high. The 2018 GM table characterizes the monitored response as a short to power on the output control circuit.

The narrow command window is significant

For this implementation, the control voltage must be above 9 V to fail. The pump is enabled, system voltage is above 10.2 V, and control PWM duty lies strictly between zero and 10 percent. Sixteen failed samples among 20 at 250-millisecond intervals satisfy the listed five-second evaluation. GM gives Type B, two-trip reporting.

This is a command-dependent electrical test. A high reading obtained with a substantially different PWM request does not, on its own, reproduce P0CEC. Nor does the monitor measure coolant flow or determine whether the pump impeller is obstructed.

Preserve control and enable as separate observations

The table distinguishes the pump's enable state from its PWM control request. Retaining both in a diagnostic record helps avoid confusing an enable-circuit problem with this control-output fault. Compare any companion cooling codes against their own measured quantities before assigning a common cause.

After the relevant circuit repair, confirmation should show acceptable feedback in the documented command window and completion of the applicable cooling-system checks. A normal coolant temperature at idle is insufficient proof that this electrical test passed. Use the vehicle-specific circuit information and qualified hybrid-system service; the table supplies neither physical pin locations nor instructions to energize the pump externally.

Source and applicability

This explanation follows the documented GM monitor, not a verified application to every vehicle with this code. Confirm the vehicle, reporting module and calibration in current service information. GM diagnostic table, physical page 945.