P257AVacuum Reservoir Control Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P257A is an output fault on the control line of the vacuum reservoir, usually a solenoid or switching valve the engine computer uses to connect, isolate or vent a vacuum storage tank. Such tanks occur mainly on diesels whose EGR valves, turbocharger vanes or flaps are worked by vacuum; GM bulletin PI1260 for the 2014 Cruze 2.0 L diesel, for example, shows the pump filling a tank built into the EGR cooler, which in turn feeds the turbo and EGR control solenoids. The driver stage logs it on an open circuit or on a fault it cannot assign to low or high. No manufacturer documents P257A publicly; CARB 13 CCR 1968.2 treats such outputs as comprehensive components to be checked for circuit faults. P257B and P257C cover shorts to ground and to voltage.
- What you may notice
- Engine warning lamp on
- Vacuum-driven actuators such as EGR or turbo vanes respond poorly
- Likely causes
- LikelyLoose or corroded connector at the reservoir control valve
- PossibleBroken wire in the control or supply line
- PossibleOpen solenoid coil in the control valve
- RareFaulty output stage in the engine control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.