P26F7: Coolant Pump C Supply Voltage Circuit

What it means

The dedicated supply voltage line to the third coolant pump module is faulty. Pump cannot operate without battery feed.

At a glance

• Usually lights the check-engine light

How it works

Coolant Pump C needs a dedicated battery supply to run its separate cooling loop. The control module monitors that supply and sets this code when the feed is missing or cannot deliver power reliably, often because of a blown fuse or a high-resistance connection.

Common causes

Most likely first.

1. Blown fuse on supply line
2. High-resistance contact in supply harness

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 check live data for Pump C command and supply status to confirm when the feed fault occurs.
2. With the system cool and switched off, inspect the pump's supply connector and harness for corrosion, looseness, damaged insulation, or heat marks.
3. Check the fuse serving the Pump C supply and verify it is intact; investigate why it opened if it is blown.
4. Measure supply voltage at the pump connector under the conditions specified by the manufacturer to find a weak feed.
5. If voltage is low, check the supply harness and connections for excessive resistance against the manufacturer's specification.

Common fixes

• Replace a blown Pump C supply fuse after checking for a short or overload.
• Clean and secure a corroded or loose supply connection.
• Repair or replace a damaged, high-resistance section of the supply harness.

Can I keep driving?

Avoid driving if a temperature warning appears or the affected cooling loop is not working; overheating can cause serious damage. If there are no temperature symptoms, keep trips short and watch the temperature warning.