P26D3: Engine Coolant Pump Supply Voltage Circuit

What it means

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

At a glance

• Usually lights the check-engine light

How it works

The coolant pump control module receives battery power through a dedicated supply circuit. P26D3 indicates a fault in that supply circuit, so the module may not receive the power it needs to run the pump.

Common causes

Most likely first.

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

Symptoms

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

How to diagnose it

1. Check freeze-frame data and live pump-module supply voltage to see whether the fault coincides with a pump command or loss of power.
2. Inspect the dedicated supply wiring, fuse, and pump-module connector for damage, corrosion, looseness, or signs of overheating.
3. Check the supply fuse for continuity and confirm that power reaches both sides under the conditions specified by the wiring diagram.
4. Measure voltage at the pump-module supply and check for voltage drop under load against the manufacturer's specification.
5. If the supply circuit tests correctly, check the module's ground connection before considering a control-module fault.

Common fixes

• Replace a blown supply fuse after checking for the cause of the overload.
• Repair damaged or high-resistance supply wiring.
• Clean or repair loose, corroded, or heat-damaged connector terminals.
• Repair a poor module ground if testing identifies one.

Can I keep driving?

The pump may lose power and cooling may fail, so avoid driving if temperature rises or a cooling warning appears. Stop safely if the engine overheats to prevent damage.