P26CF: Engine Coolant Pump Control Module System Voltage

What it means

The integrated controller of the smart coolant pump reports a system voltage out of operating range.

At a glance

• Usually lights the check-engine light

How it works

The smart engine coolant pump has an integrated control module that monitors its electrical supply while operating the pump. P26CF indicates that the module reports system voltage outside its operating range, without specifying whether it is too low or too high.

Common causes

Most likely first.

1. Weak battery sags voltage under pump load
2. Alternator output out of regulation

Symptoms

• Check-engine light may be on
• Engine temperature may rise
• Cooling-system warning or reduced-power message may appear

How to diagnose it

1. Record freeze-frame data and monitor pump-module voltage, battery voltage, and charging-system data to see when the out-of-range condition occurs.
2. Inspect the battery terminals, pump-module connector, and related wiring for looseness, corrosion, or damage that could disturb the supply.
3. Have the battery tested under load, since a weak battery may sag when the pump operates.
4. Check alternator output and regulation under the conditions shown in the freeze-frame data against the manufacturer's specification.
5. If battery and charging tests are normal, check the pump-module power and ground connections for voltage drop before condemning the module.

Common fixes

• Clean and secure loose or corroded battery terminals and pump-module connections.
• Replace a battery that fails its load test.
• Repair charging-system wiring or replace a faulty alternator or regulator if output is out of specification.
• Repair a poor pump-module power or ground connection.

Can I keep driving?

The pump may be limited or disabled, so avoid driving if engine temperature rises or a cooling warning appears. Stop safely if it overheats, since continued high temperature can damage the engine.