What it means
The smart coolant pump module reports the system voltage above operating range. Pump output is reduced or disabled to protect the module.
At a glance
- Usually lights the check-engine light
How it works
The smart coolant pump's integrated control module monitors system voltage to protect itself and operate the pump. P26D1 specifically indicates voltage above the module's operating range, which can result from excessive charging voltage or a supply wire shorted to a higher-voltage circuit.
Common causes
Most likely first.
- Alternator regulator failed to limit output
- Load dump transient after disconnecting a heavy load
Symptoms
- Check-engine light may be on
- Engine temperature may rise
- Cooling-system warning or reduced-power message may appear
How to diagnose it
- Check freeze-frame data and live pump-module and battery voltage to establish whether the high reading coincides with engine or charging-system operation.
- Inspect the pump-module supply harness and connector for damaged insulation, cross-contact with another power wire, corrosion, or loose pins.
- Check charging-system output and regulation against the manufacturer's specification, including under changing electrical loads.
- If charging voltage is within specification, trace the pump supply wire for an unintended connection to a higher-voltage circuit.
- Inspect connector terminals for corrosion or poor contact and verify supply voltage at the module against the wiring diagram.
Common fixes
- Repair damaged supply-wire insulation or a short to a higher-voltage circuit.
- Clean or repair corroded or loose pump-module connector terminals.
- Repair or replace the alternator or regulator if charging output exceeds specification.
Can I keep driving?
The module may limit or disable pump operation, so avoid driving if engine temperature rises or a cooling warning appears. Stop safely if it overheats; excessive charging voltage can also affect other electrical components.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.