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 The ECM cannot energise the actuator, so vacuum is no longer maintained on demand and consumers like brake booster, EGR or HVAC dampers may run out of vacuum.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Open control wireCommon
- Failed driver in the control modulePossible
- Pin pushed back out of connector bodyLess likely
Parts involved
- Vacuum Reservoir Control Valve
- Wiring Harness
P257A is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.