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

P23A2

Exhaust Heat Exchanger Bypass Valve B Control Circuit Open

An open circuit is detected on the control line for the bypass flap A of the exhaust heat exchanger. This valve directs exhaust either through the heat exchanger (cold start, fast warm-up) or around it (normal operation). Without working control the warm-up strategy is impaired and emissions during cold start increase.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number3 / A2

Possible causes

  • Open in harness or actuator high
  • Pin pushed back out of connector body low
  • Cracked solder joint inside the module or sensor low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 200–700 €
  • Estimated time: 1–2.5 h
  • Component: exhaust bypass valve b
  • MIL / check engine light
  • emissions-relevant

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