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

P257A

Vacuum Reservoir Control Circuit/Open

The control circuit that drives the vacuum reservoir control valve (or vacuum pump motor) is open. The ECM cannot energise the actuator, so vacuum is no longer maintained on demand and consumers like brake booster, EGR or HVAC dampers may run out of vacuum.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 7A

Possible causes

  • Open control wire high
  • Failed driver in the control module medium
  • Pin pushed back out of connector body low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 120–600 €
  • Estimated time: 0.5–2 h
  • Component: vacuum reservoir control valve
  • Component: wiring harness
  • 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