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Dagumpf Dagumpf is offline
Posts: 29
Join Date: Dec 2018
Car: BMW E93 N54 2009
Default MSD81 Low Pressure Fuel Sensor voltage problems - 08-25-2019, 04:43 AM

After much diagnosis, I have figured out there is something wrong with the voltage signal from the DME to the low pressure fuel sensor.

On the X60005 connector at the DME, pin 7 is Ground Low Pressure sensor, pin 8 is Supply Low Pressure Sensor and pin 34 is Signal Low Pressure Sensor.

I disconnected just the three sensor wires at the DME, and then measured the voltages coming from the DME.

Measuring pin 8 (Supply) to chassis give a perfect 5.00V. Measuring ground to chassis jumps around, normally between 1.2 and 3V. So this looks like a DME fault.

Can this be repaired? If so, how?

Further background: After driving through a large puddle (accidentally), I caused some other electrical damage, including blowing the radiator fan. After repairing that, I also discovered a silent 29FE fault, referring to a faulty low pressure sensor. This fault doesn't affect the operation of the car, as it just runs the Low Pressure Fuel Pump flat out. I replaced the sensor, and he fault did not go away. Hence I began an electrical diagnosis, leading to the above.


Low pressure fuel system

BMW E93 335is Convertible
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