[gtmax500]

Hey Guys,

This is probably going to be a pretty unique DIY but hopefully it helps someone out. So I installed a hitch on my 235 so I could use a hitch mounted bike rack since I didn't want to do anything with my roof, the only problem is when you back up the PDC thinks you're right behind something so it blares the PDC noise really loudly and is super annoying. I always had to just deal with it or press the PDC button and loose my backup camera as well. I really just hated pressing the button every time I put it in reverse.

To solve this I figured there must be a way to just disable the ultrasonic sensors with a switch or something and so that's what I did.

First I went to this website www.newtis.info which basically has every wiring diagram and component description of our whole car. It's a pretty amazing website. I looked up the wiring diagram for the F22 M235 and found that the PDC is controlled by the Rear Electronic Module. You can find the diagram for the ultrasonic sensors here. All of the rear USs share a common power and ground so I figured I could just add an On-Off switch inline with the power wire.

You can find the pin-out for the REM here and if you scroll down you'll see that the USs are on plug A174*14B and pins 38, 39, 50, 51 with the power and ground being pins 49 and 37 respectfully. This picture shows where the REM is and which plug is A174*14B. You can find all these links by clicking around on the wiring diagram. It really is a super useful site.

Remember: before you start doing anything with the car you should always remove the negative battery cable just in case.

Since its in the trunk you first have to remove all of the bottom and passenger side trim. I wont go into detail since its really easy. This is what you should get down to:



The REM is the black box with all the plugs and according to the link above the plug we want should be the top one.



To remove the plug you have to press down on the little black tab and rotate the white bracket (for lack of a better term) down. It's pretty self explanatory. You'll then want to remove the inner connectors by prying each side and sliding the inner connectors out like this:



The brown connector is what we want. Each connector has tiny numbers on them that tell you which pin goes to which number from the pinout diagram I linked to above. Remember we want pin 49 which is this one:



Notice it is a green wire with a black stripe. To remove it you have to press down on the little latch like the picture above and slide the pin out. It will get caught on the next little ledge so you'll have to press down on the latch again to pull it out. It should come out very easily so DO NOT pull very hard on the wire, you don't want to rip off the connector. If it doesn't come out easily you aren't pushing down on the latch properly.



Technically you don't have to take the pin out but it makes it way easier. Now give yourself some room and push the wire through the little black wrapping so you have more length to work with and snip it somewhere in the middle:



I used the little crimp splicers but you can use whatever method you'd like to connect about a foot of wire to each side:



Do the same thing with the other side of the wire. I put heat shrink tubing over the connector just to hold the wires a little better and then wrapped them up with electrical tape. Slide the inner connectors back into the plug (don't worry they only go in one way) and insert the plug back into the REM.



Now you're ready to put all the trim back together or make a hole in the trim for the switch if you know where you want it to go. I didn't know where I wanted it so i put the trim back in and found a good spot. I decided to place my switch right between these two holes in the trim because there was nothing behind it.



I then crimped on spade connectors so I could connect the wires to the switch. As you can see the spot I chose for the switch is not the best because the connectors bump up against the body but it'll work.



And that's it. Connect the battery back up and you're good to go. Now when you disable the PDC sensors you're car will throw an error but it really doesn't matter. Also, even though you only disabled the rear USs since the car thinks there is a fault it disables the fronts as well but that is not an issue for me either. The main advantage is it stops the terribly loud beeping and I can still use the back up camera.



Hope this DIY helps someone who might be in a similar situation. I am very glad I found the website with all the wiring diagrams and information as I think that will be an extremely useful resource in the future and the best part is its free!

Let me know if you have any questions and Ill try and help you out.

Cheers!

[BEM-S4]

I just bought this for my X5 winter beater, installing this weekend.

https://fensens.com

[M2Rob]

Love the post. Very informative. But, doesn't this do the same thing as the PDC off button that you can buy from ECS? Seems buying that center console button would be much easier and cleaner.

[gtmax500]

Originally Posted by M2Rob

Love the post. Very informative. But, doesn't this do the same thing as the PDC off button that you can buy from ECS? Seems buying that center console button would be much easier and cleaner.

Thank you! And hmmm, I am not aware of any PDC off button but that seems interesting. Got a link?

[M2Rob]

My understanding is all 2er are prewired for this switch, and it is plug and play. And there is a thread on this forum for install.

https://www.ecstuning.com/b-genuine-...t/61319252912/

[gtmax500]

Oh I already have that button by my shifter. I have to press that button every time I shift into reverse and I loose my backup camera. With the button I installed I switch it once and the PDC beeps don't come on untill I switch it off no matter how many times I shift into reverse and I keep my camera.

[Doubledeuce06]

Originally Posted by gtmax500

Hey Guys,

This is probably going to be a pretty unique DIY but hopefully it helps someone out. So I installed a hitch on my 235 so I could use a hitch mounted bike rack since I didn't want to do anything with my roof, the only problem is when you back up the PDC thinks you're right behind something so it blares the PDC noise really loudly and is super annoying. I always had to just deal with it or press the PDC button and loose my backup camera as well. I really just hated pressing the button every time I put it in reverse.

To solve this I figured there must be a way to just disable the ultrasonic sensors with a switch or something and so that's what I did.

First I went to this website www.newtis.info which basically has every wiring diagram and component description of our whole car. It's a pretty amazing website. I looked up the wiring diagram for the F22 M235 and found that the PDC is controlled by the Rear Electronic Module. You can find the diagram for the ultrasonic sensors here. All of the rear USs share a common power and ground so I figured I could just add an On-Off switch inline with the power wire.

You can find the pin-out for the REM here and if you scroll down you'll see that the USs are on plug A174*14B and pins 38, 39, 50, 51 with the power and ground being pins 49 and 37 respectfully. This picture shows where the REM is and which plug is A174*14B. You can find all these links by clicking around on the wiring diagram. It really is a super useful site.

Remember: before you start doing anything with the car you should always remove the negative battery cable just in case.

Since its in the trunk you first have to remove all of the bottom and passenger side trim. I wont go into detail since its really easy. This is what you should get down to:



The REM is the black box with all the plugs and according to the link above the plug we want should be the top one.



To remove the plug you have to press down on the little black tab and rotate the white bracket (for lack of a better term) down. It's pretty self explanatory. You'll then want to remove the inner connectors by prying each side and sliding the inner connectors out like this:



The brown connector is what we want. Each connector has tiny numbers on them that tell you which pin goes to which number from the pinout diagram I linked to above. Remember we want pin 49 which is this one:



Notice it is a green wire with a black stripe. To remove it you have to press down on the little latch like the picture above and slide the pin out. It will get caught on the next little ledge so you'll have to press down on the latch again to pull it out. It should come out very easily so DO NOT pull very hard on the wire, you don't want to rip off the connector. If it doesn't come out easily you aren't pushing down on the latch properly.



Technically you don't have to take the pin out but it makes it way easier. Now give yourself some room and push the wire through the little black wrapping so you have more length to work with and snip it somewhere in the middle:



I used the little crimp splicers but you can use whatever method you'd like to connect about a foot of wire to each side:



Do the same thing with the other side of the wire. I put heat shrink tubing over the connector just to hold the wires a little better and then wrapped them up with electrical tape. Slide the inner connectors back into the plug (don't worry they only go in one way) and insert the plug back into the REM.



Now you're ready to put all the trim back together or make a hole in the trim for the switch if you know where you want it to go. I didn't know where I wanted it so i put the trim back in and found a good spot. I decided to place my switch right between these two holes in the trim because there was nothing behind it.



I then crimped on spade connectors so I could connect the wires to the switch. As you can see the spot I chose for the switch is not the best because the connectors bump up against the body but it'll work.



And that's it. Connect the battery back up and you're good to go. Now when you disable the PDC sensors you're car will throw an error but it really doesn't matter. Also, even though you only disabled the rear USs since the car thinks there is a fault it disables the fronts as well but that is not an issue for me either. The main advantage is it stops the terribly loud beeping and I can still use the back up camera.



Hope this DIY helps someone who might be in a similar situation. I am very glad I found the website with all the wiring diagrams and information as I think that will be an extremely useful resource in the future and the best part is its free!

Let me know if you have any questions and Ill try and help you out.

Cheers!

Can you just remove that power wire and wrap it up in electrical tape or something if you want to turn PDC off and you don’t care about having a switch?

[gtmax500]

Originally Posted by Doubledeuce06

Can you just remove that power wire and wrap it up in electrical tape or something if you want to turn PDC off and you don’t care about having a switch?

Yes you can just remove the wire and the PDC will not work. You'll still get the error code though.