P2603

Coolant Pump A Control Circuit High

Q: 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.

Q: 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.

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.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P2603 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX