Powertrain, generic (extended)

P257A Vacuum Reservoir Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Loose or corroded connector at the reservoir control valve
Broken wire in the control or supply line
Open solenoid coil in the control valve
Faulty output stage in the engine control module

Symptoms

  • Engine warning lamp on
  • Vacuum-driven actuators such as EGR or turbo vanes respond poorly

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–300
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

vacuum reservoir control valvewiring harness

Related codes

P257BP257CP2525P2526

References: law.cornell.edu, static.nhtsa.gov.