P258CVacuum Pump Control Circuit A Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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.
- What you may notice
- Engine or brake warning lamp on
- Pump silent or running constantly
- Firmer brake pedal
- Likely causes
- LikelyControl or relay wire shorted to ground
- PossibleBlown vacuum pump fuse
- PossibleFaulty pump relay or relay coil
- 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: €20 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.