Powertrain, generic (extended)

P258C Vacuum Pump Control Circuit A Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P258C reports that control circuit A of the electrically driven vacuum pump reads too low, typically because the control or relay line is shorted to ground, the relay coil is faulty, or a blown supply fuse leaves the monitoring line without voltage. Depending on how the circuit is laid out, the pump may then run nonstop or not at all. No manufacturer publishes P258C itself. Ford's hybrid OBD summary shows the kind of window used on this circuit for P258A and P258B: the monitoring voltage should stay between 1.3 and 5.0 V with the relay off and must not drop below 250 mV with it on. CARB 13 CCR 1968.2 treats such electrical outputs as comprehensive components. P258A is the open circuit, P258D the high side; if braking assist suffers, P050F for low brake vacuum can follow.

Likely causes

Control or relay wire shorted to ground
Blown vacuum pump fuse
Faulty pump relay or relay coil

Symptoms

  • Engine or brake warning lamp on
  • Pump silent or running constantly
  • Firmer brake pedal

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–600
Time0.3–2.5 h

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

Parts involved

vacuum pumpwiring harness

Related codes

P258AP258BP258DP25F0P050F

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