P2603
Coolant Pump A Control Circuit High
Engine cooling
Generic OBD-II
Medium
What it means
P2603 means the PCM detected high voltage (typically an open circuit) in the control circuit for auxiliary coolant pump A. This electric pump helps move coolant for the engine or turbocharger, so the risk is reduced cooling if the pump does not run. It is an electrical circuit fault and will not prevent the engine from starting.
Medium
Can I keep driving? Drivable, but if the auxiliary coolant pump stops running the engine or turbo can overheat — watch the temperature gauge and stop if it climbs.
Common symptoms
What you'll notice
- Check-engine light on
- Engine or turbo running hotter than normal
- Coolant pump not running when it should
- Often no drivable symptom beyond the warning light
Common causes
Most likely first
- Open circuit or high resistance in the pump's control wiringLikely
- Failed electric auxiliary coolant pumpCommon
- Corroded or disconnected connector at the pump or PCMCommon
- Blown fuse or failed relay in the pump circuitLess often
- Faulty PCM output driver (least likely)Less often
How to diagnose & fix
Work through it in order
- Confirm the code and check for related overheating or coolant-temperature codes.
- Inspect the coolant pump connector and wiring for open circuits, corrosion, or damage.
- Verify power and ground at the pump; check its fuse and relay.
- Command the pump with a scan tool and confirm it runs and moves coolant.
- Replace the pump if it fails with good supply and ground; otherwise repair the circuit. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2603?+
Short-term yes, but keep an eye on the temperature gauge. An auxiliary coolant pump that will not run can let the engine or turbocharger overheat during hard use or idling.
Can I just clear P2603?+
It returns until the wiring or pump is fixed. Clearing does not restore coolant flow or address the electrical fault.
Related codes
Often seen with P2603
Read & clear P2603 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX