What does code P2603 mean?

Q: What does code P2603 mean?

Coolant Pump Control Circuit High. P2603 indicates that the engine control module (ECM) has detected an abnormally high voltage on the control circuit for the engine coolant pump, which is typically a pulse-width modulated (PWM) signal used to regulate pump speed. The ECM expects a specific voltage range on this circuit, and a reading above the threshold suggests an open circuit, a short to voltage, or a faulty pump control module.

DTC codes / P26xx · Computer and output circuits / P2603

P2603Coolant Pump Control Circuit High

P2603 indicates that the engine control module (ECM) has detected an abnormally high voltage on the control circuit for the engine coolant pump, which is typically a pulse-width modulated (PWM) signal used to regulate pump speed. The ECM expects a specific voltage range on this circuit, and a reading above the threshold suggests an open circuit, a short to voltage, or a faulty pump control module.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaComputer and output circuits

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.