What does it mean?
P1251 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Pressure Regulator Control Solenoid Circuit Malfunction .
Symptoms
- The MIL is on and the fuel system runs on a default pressure strategy
- Long cranking, hard hot starting, or refusal to start in the worst case
- Rough idle and misfire, especially under load
- Reduced power and poor acceleration
- Smell of unburnt fuel or visible smoke on some applications
- Higher than normal fuel consumption
Likely causes
- Open winding inside the regulator control solenoid
- Solenoid control wire shorted to ground or to battery voltage through a chafed loom
- Corroded or water-damaged connector at the solenoid
- Missing supply voltage because of a blown fuse or a failed relay contact
- High resistance in the ground path shared with other fuel system actuators
- Damaged pins or a partially seated connector after previous work in the area
- Module output driver failure, considered only once the external circuit is proven
How to fix it
- Confirm the code with the scan tool and check whether it sets as an open circuit or as a short by watching the circuit status in live data
- Command the solenoid on and off with the actuator test and listen or feel for it operating
- Unplug the solenoid and measure its winding resistance against the specified value; an infinite reading proves an open winding
- Check for battery voltage on the supply pin of the connector with the ignition on, and test the fuse and relay feeding it
- Measure the control wire back to the module for continuity and for shorts to ground or voltage
- Repair any harness or connector faults found and retest before replacing parts
- Replace the pressure regulator control solenoid if it fails the resistance and activation checks, then clear the code and verify fuel pressure control