What does it mean?
P1236 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Electrical Fuel Pump Short to Ground or Open Circuit .
Symptoms
- Crank but no start, or the engine starts and immediately stalls
- No pump prime heard from the tank at key on
- Fuel rail pressure at zero or dropping rapidly
- Repeatedly blown fuel pump fuse
- Check engine lamp on, often with lean or fuel pressure codes
- Stalling over bumps or when the fuel level is low
Likely causes
- Broken wire or a corroded joint between the relay, module and pump
- Corroded or burnt terminals in the pump flange connector on the tank
- Pump feed wire chafed against the underbody or a tank strap and shorted to ground
- Seized or worn pump motor drawing excessive current and blowing the fuse
- Poor pump ground at the flange or at the body stud
- Blown fuse or a relay that no longer passes current
- Module output stage failure
How to fix it
- Check the pump fuse and relay first, and note whether the fuse blows again straight away
- Read fuel rail pressure and listen for prime to confirm the pump is not running
- Back-probe the pump connector while cranking and check supply voltage and ground
- Voltage drop test the pump ground path
- With the pump unplugged, test the feed wire for continuity to the relay and for a short to ground
- Measure pump current draw; a motor above specification is failing and will blow fuses again
- Renew the pump if it is drawing high current or is open, and repair any damaged wiring before refitting
- Check the module output only after the circuit and pump have been proven