P26D4
Engine Coolant Pump Supply Voltage Circuit Low
The dedicated supply voltage to the coolant pump module is below 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.
- High-resistance battery feedCommon
- Weak battery sags under pump currentPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Smart Coolant Pump Module
- Supply Circuit
- Battery
P26D4 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.