Q: accidentally hooked up jumper cables backwards. No there is no spark on plugs and the fuel pump is running with the engine off.

asked by on December 07, 2016

hi my battery was going dead old battery so i went to jump it and by mistake with my small jumper i hooked it up wrong and real quick put it and off and i herd the spark after this the car did't start. i replaced the battery and starter and one relay in the front compartment becouse it was buzzing. Now the car cranks but it not giving me any spark.The code reader showing me DTC module U114B U115E U115B U114E.and Fuel pump. About the fuel pump, I can hear it running on and off when the car is off.What controls the pump to go on and off.

My car has 107356 miles.
My car has an automatic transmission.

Hi there. The U codes are for the body portion of the electrical system. U114 codes are designated to the fuel system. If the fuel pump is working but all of a sudden it is coming on when the engine is off, then there is a major short in the electrical system of the vehicle. The U115 codes relate to the PCM (computer) not working properly. Since jumper cables were hooked up backwards, the shock of the power most likely burned up the PCM (computer) to the car. I recommend replacing the PCM (computer) and installing a new battery. If you need further assistance with your electrical system, then seek out a professional, such as one from Your Mechanic, to help you.

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Hello - the engine management computer controls the fuel pump (through a relay). The lack of spark may be related to a failed crankshaft position sensor, or possibly one or more of the coil packs. Failure of these will yield a "no spark" condition. The codes you list are "BMW-proprietary", making them less useful. Further diagnosis is needed to work back up the "ignition" path to determine the failed component. I would recommend an engine ignition system inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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