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P2602 — Coolant Pump Control Circuit Low

Manufacturer-specificPowertrain (engine & transmission)

P2602 indicates that the engine control module has detected a low voltage condition in the coolant pump control circuit, meaning the coolant pump is not receiving the proper signal to operate.

Symptoms

What causes it — most likely first

1. Faulty coolant pump relay or solenoid

A malfunctioning relay or solenoid can prevent the pump from receiving power, causing a low voltage reading.

2. Wiring or connector issue in the coolant pump circuit

Damaged, corroded, or broken wiring or a loose connector can interrupt the signal to the pump.

3. Defective coolant pump control module (PCM) or wiring harness within the module

If the PCM or its internal circuitry cannot generate the correct control voltage, the pump will not activate.

4. Mechanical failure of the coolant pump itself

A seized or damaged pump may draw excessive current, leading to a voltage drop in the control circuit.

5. Short or open circuit in the coolant pump power wire

An unintended short or open can alter voltage levels, triggering the low‑voltage code.

How it's diagnosed

  1. Check the coolant pump relay or solenoid for proper operation and continuity.
  2. Inspect the wiring harness and connectors for damage, corrosion, or loose connections.
  3. Test the voltage at the coolant pump control circuit while the engine is running to confirm a low voltage reading.
  4. Use a multimeter to verify the PCM’s output signal to the pump.
  5. Examine the coolant pump for mechanical integrity and electrical resistance.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)
Related codesP2600 — Coolant Pump Control CircuitopenP2601 — Coolant Pump Control Circuit PerformanP2603 — Coolant Pump Control Circuit HighP2604 — Intake Air Heater Circuit RangeperformP2605 — Intake Air Heater B CircuitopenP2606 — Intake Air Heater B Circuit Rangeperfo

Frequently asked

Is the PCM usually the problem for P2602?

No, the PCM is rarely the cause. Most often the issue is a faulty relay, damaged wiring, or a malfunctioning pump. The PCM is only considered after the hardware has been ruled out.

Why does the coolant pump not run when the engine is warm?

The pump is designed to operate only after the engine reaches a certain temperature; if the control circuit shows low voltage, it may fail to activate even when needed.

Can a blown fuse cause P2602?

Yes, a blown fuse in the coolant pump circuit can result in a low voltage condition and trigger the code.