OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

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.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number6 / D4

Possible causes

  • High-resistance battery feed high
  • Weak battery sags under pump current medium
  • Connector pins corroded - high contact resistance low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 80–600 €
  • Estimated time: 0.5–2.5 h
  • Component: smart coolant pump module
  • Component: supply circuit
  • Component: battery
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication