What does it mean?
P1225 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 1 Fuel Injection Circuit Short to Ground .
Symptoms
- Check engine lamp on, sometimes with a blown injector fuse and several cylinders dead
- Misfire, shaking and rough idle centred on cylinder 1
- Overfuelling: black smoke, fuel smell, wet plug and possible fuel in the oil
- Loss of power and poor starting
- On some vehicles the engine will not start at all when the fuse has blown
Likely causes
- Injector wire chafed against the cylinder head, a bracket or the engine block
- Injector winding shorted to the injector body or its metal housing
- Coolant or water in the connector giving a path from the control pin to earth
- Loom pinched between the intake manifold and the head during a previous repair
- Damaged wire under a clip where vibration has worn away the insulation
- Injector driver in the module destroyed by the ground short, which often blows the injector fuse as well
How to fix it
- Check the injector fuse first, since a ground short frequently takes it out
- Unplug the injector and measure resistance from the control wire to ground; a low reading confirms the short
- Trace the harness along the head and manifold looking for chafe against metal and pinch damage
- Inspect the connector for coolant and corrosion, and measure from the injector pins to its body
- Compare injector resistance readings across all cylinders
- Repair the harness and insulate it away from the contact point, then retest before fitting parts
- Renew the injector if it is shorted to its body, and check the module driver last