I changed out the low pressure fuel sensor on this A4 Audi trying to resolve a P0089 error code. I will be writing a post about this entire process, but this was one of the parts I replaced. It was not the issue, but some internet research stated it was a possible cause and for $30 was worth a try. In my opinion, and in hindsight, it was a waste of money since the sensor was actually reading a pressure value, indicating that it was working properly. But since the car seemed to run fine, and up to this point there have not been any issues, I thought that the sensor may have been faulty.
It will take a little bit of work to get this replaced, but it should not take you too long. The first thing that you will need to do, is to remove the vent hose that is attached to the intake; this is part of the PCV system, and this side of it just needs to be disconnected and routed out of the way.
Squeeze the plastic clips and pull the vent hose out. It is routed underneath the main incoming fuel line so you will need to maneuver it out of the car, being careful of the fuel line. If you found this too difficult, you could even disconnect the fuel line to make removal even easier.
There is a bracket that is holding the main fuel line coming from the rear of the car. It is strictly there for routing purposes but it is kind of in the way. Use a 10mm open ended wrench to remove the 10mm bolt that is holding this bracket in place. You may be able to remove the low pressure fuel sensor without removing the bracket but it doesn’t take long to remove this piece, and it makes the job much easier.
Pull off the electrical connector that is connected to the low pressure fuel sensor and route it out of the way to avoid damaging it. In this particular case, the clip was broken and I was able to just slide it off, in most cases you will want to push down on the clip and pull it off. This one must have been difficult in the past since its clip was broken.
You should now be able to get a wrench in there to remove the sensor. I used an open ended wrench which was able to turn this sensor. I was able to get a 15/16 inch wrench on the sensor and break it loose. Once you break it loose, you should be able to just turn it by hand and remove it.
Putting the new sensor in is the exact opposite of the removal. Just screw the sensor into the low pressure side of the high pressure fuel pump and attach the electrical connector before re-assembling everything else.