P26FA: Coolant Pump C Overspeed/Air in System

What it means

The third coolant pump speed feedback is higher than commanded with no resistance from coolant. Indicates air in the cooling loop or low coolant level so the pump spins free.

At a glance

• Usually lights the check-engine light

How it works

Coolant Pump C circulates coolant through a separate loop, and the control module compares its speed feedback with the commanded speed. This code sets when the pump reports overspeed consistent with little coolant resistance, often because the loop is low on coolant or has trapped air.

Common causes

Most likely first.

1. Low coolant level due to leak or improper fill
2. Air pocket trapped in the cooling loop

Symptoms

• Engine or powertrain warning light may come on
• Temperature warning may appear if the affected cooling loop overheats
• Cooling performance may be reduced in the affected system

How to diagnose it

1. Record freeze-frame data and compare Pump C commanded speed with reported speed and loop temperature in live data.
2. With the system fully cool, check the coolant level in the affected loop using the vehicle's specified reservoir or service point.
3. Inspect the loop, hoses, pump, and connections for leaks that could explain low coolant.
4. If the level is low, correct it with the specified coolant and follow the manufacturer's filling procedure for that loop.
5. If the level is correct, bleed trapped air using the manufacturer's procedure, then recheck pump speed and temperature.

Common fixes

• Repair a leak in the affected cooling loop and refill it with the specified coolant.
• Bleed air from the loop using the manufacturer's procedure.
• Correct an improper fill that left the loop low or air-bound.

Can I keep driving?

Do not drive if the coolant level is low, a temperature warning appears, or the affected loop is overheating; pump overspeed from air or low coolant can leave components without adequate cooling. Check only after the system has cooled.