Code Definition

P2603 — Electric Coolant Pump Command Circuit/Open

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P2603

P2603 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2603 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P2603 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Engine Control Module (ECM) controls the electric coolant pump via a dedicated command circuit to regulate coolant flow based on engine temperature and operating conditions. DTC P2603 is set when the ECM commands the electric coolant pump ON or OFF but detects an open circuit or no electrical response in the pump command circuit, typically identified by missing current draw or an implausible feedback voltage. This prevents the ECM from controlling coolant circulation as intended and can result in elevated coolant temperatures, particularly during high load or post shutdown soak periods. Th...

Join TaT to view the complete code information and diagnostic details.

Quick Facts