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

P26A3

Engine Coolant Bypass Valve A Range/Performance

The coolant bypass valve A responds to commands but the resulting coolant temperature behaviour is not as expected. Possibly stuck partially open or contaminated bore.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number6 / A3

Possible causes

  • Valve partially stuck by sediment high
  • Weak return spring fails to close fully medium
  • Sensor element aged beyond calibration window low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 150–1000 €
  • Estimated time: 1–3.5 h
  • Component: coolant bypass valve a
  • Component: thermostat housing
  • 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