P26D5
Engine Coolant Pump Supply Voltage Circuit High
The dedicated supply voltage to the coolant pump module is above operating range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Alternator regulator failed to limit outputCommon
- Wiring shorted to a higher-voltage circuitLess likely
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Smart Coolant Pump Module
- Supply Circuit
- Charging System
P26D5 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.