P2602 – Coolant Pump A Control Circuit Low (OBD2)
P2602 means "Coolant Pump A Control Circuit Low". The voltage the control unit measures in the electric coolant pump circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.
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P2602 quick summary
| Fault code | P2602 |
|---|---|
| Meaning | Coolant Pump A Control Circuit Low |
| System | Powertrain (Engine & Transmission) |
| Vehicles | Generic OBD2 |
| Severity | High |
| Can I drive? | Not recommended if it is the main coolant pump – watch the temperature gauge and stop at once if it rises. An auxiliary pump fault usually allows careful driving. |
| Repair cost | €100 – €900 |
How the electric coolant pump works
Many modern engines use an electrically driven coolant pump controlled by the engine control unit; these codes mean the pump's control circuit or performance is faulty.
An electric coolant pump can run at variable speed – or stop completely – independent of engine speed. That lets the engine warm up faster, cool the turbocharger after switch-off and save fuel. On some engines it replaces the belt-driven water pump completely; on others it is an auxiliary pump for the heater, turbo or intercooler.
The control unit drives the pump with a PWM signal and receives feedback on speed, current or faults. Codes report an open, low or high control circuit and a pump that does not reach the commanded speed.
Pumps fail because of worn bearings, electronics failures, air in the cooling system or coolant leaking into the electronics. A failed main pump can make the engine overheat within minutes.
Symptoms of P2602
- Engine overheating or temperature warning
- Reduced power to protect the engine
- Heater blows cold
- Check Engine light
- Coolant level dropping or coolant around the pump
Most common causes of P2602 (most likely first)
Mechanic's Pro Tip
After replacing an electric coolant pump, always run the manufacturer's bleeding routine with the scan tool. An air pocket can make the new pump report a fault or let the engine overheat.
1.Signal or control wire shorted to ground
Most likelyLook for chafed insulation where the harness touches the engine, exhaust brackets or body edges.
2.Missing 5 V reference or supply voltage
An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.
3.Internal short in the electric coolant pump
4.Failed electric coolant pump
Bearings or electronics fail with age.
5.Air in the cooling system
Can make the pump run dry and report a fault.
6.Corroded connector or wiring fault
7.Blown fuse or faulty relay
Step-by-step diagnostic guide
- 1
Read codes and watch temperatures
Read all codes and watch coolant temperature and pump command/speed in live data.
- 2
Measure the signal voltage
With the ignition on and the electric coolant pump plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.
Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.
- 3
Check coolant level and bleeding
Check the coolant level and bleed the system – many vehicles have a scan tool bleeding routine that runs the pump.
- 4
Check fuse, supply and control signal
Measure the pump supply and ground and check the control signal.
Multimeter: Supply near battery voltage; PWM control signal changing with the command.
- 5
Run the pump test
Use the scan tool's actuator test to run the pump and listen or feel for flow.
- 6
Replace and bleed
Replace the pump, refill with the correct coolant and run the bleeding routine.
Frequently asked questions
Can I keep driving with P2602?
Not recommended if it is the main coolant pump – watch the temperature gauge and stop at once if it rises. An auxiliary pump fault usually allows careful driving.
How much does it cost to fix P2602?
Typical repair costs are 100 € – 900 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the electric coolant pump. Always confirm the cause with the tests above before buying parts.
Can I drive with an electric coolant pump fault?
If it is the main coolant pump, only with extreme care and while watching the temperature – it can overheat the engine quickly.
Why does the pump run after I switch off the engine?
Many engines run the pump after switch-off to cool the turbocharger. That is normal.
What is the difference between P2602 and similar codes?
P2602 belongs to a group of codes for the same component that differ in the type or location of the fault: P2600 – Coolant Pump A Control Circuit/Open; P2601 – Coolant Pump A Control Range/Performance; P2603 – Coolant Pump A Control Circuit High. The tests on this page apply to the whole group; the type of fault tells you where to start.
Related fault codes
This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.