I think my Body Control Module is flaky and I would like to change it. I understand it is behind the glove box. Is it difficult to remove? What is the procedure to remove it?
I wanted to get it out so I could get the proper part numbers off of it and buy a replacement.
Thanks in advance for your assistance!
David

 

The X350 does not have a body control module behind the glove box, nor anywhere else. What errors make you suspect a faulty control module?

 

There is a Front Control Module, and a Rear Control Module, and an Air Suspension Module

 

Hi flatsix! Thanks for the response!

The symptoms I have are as follows, headlights do not work, turn signals do not work, power windows do not work, no interior lights, can't open the glove box.

It all started a few weeks ago the alarm went off for no apparent reason. After that the headlights etc. did not work. I attempted to reset the computer. I removed the battery cables and touched them together. While they were touching I turned on the ignition key for a minute or so. Then I turned off the key and re-attached the battery cables. I turned on the ignition and after a few seconds the interior lights came on, headlights worked, everything seemed to be fine. A few days later everything quit working again. This time the reset procedure did not work. I have removed and cleaned as many body grounds as I could find to no avail. It starts, drives A/C works. Battery is new and has 12.6 volts across the terminals when engine is not running.

Any suggestions? Some where I read a thread that the front control module may be at fault. Sorry I called it the wrong thing when I said body control module.

Where is the front control module located?

Once again thanks or your help!

David

 

Hi David,

from the symptoms you describe, I would consider CU replacement as the last option. I still believe that the car has a ground or low current problem. Measuring 12.6 V at the battery terminals is fine but does not proof that the input voltage at any CU is within the expected range.

I have the following recommendations:

- Go to Jagrepair.com and download the wiring diagram for your X350 and year of make. In the wiring diagram you will find all the CUs and ground points with their locations listed and of course the circuits of al the components.

- Find an opportunity to diagnose the vehicle with SDD. SDD allows a symptom-based troubleshooting and provides very differentiated error codes, which makes it easier to find the causes.

- Concentrate on the failed headlamps and trace the path of the current from the light switch via the instrument cluster and the front electronic module and the relays to the main headlamp. Somewhere along the way there must be an interruption at the input or output of one component. Non matter whether you start at the switch or if you go backwards from the headlamps.
Also check the ground supply of the instrument cluster and front electronic module.

-Unfortunately, not all input and output pins of the control units are always listed with their assignment in the wiring diagram. but if you got an error code, there are also a pinpoint test with which you can measure the functions of the components.


Fritz

 

Hi Fritz,

Thank you for the advice. I very much appreciate your time and effort. I have checked and cleaned as many of the grounds as I can get at, to no avail. I even added a wire from the grounds by the headlights to the steel screw on the headlight bracket as someone suggested. I have downloaded the wiring diagrams and a complete service manual with all the point to point wiring measurements. It is a bit over my head unfortunately.

This car has 30,000 miles and has been totally garaged its whole life.

I keep finding more things that do not work. Headlights, turn signals, electric seats, interior lights, power windows, mirror adjustments, can't open the glove box door.

When you say "check the grounds", I have been removing the nut and sanding the terminal flat surfaces as well as the surface on the ground studs that contact the terminals. None of the grounds have shown any significant corrosion, but I do know that aluminum oxide is a poor conductor.

Once again I appreciate your help and insight. Any other thoughts you may have I will also look into.

Thanks Fritz!

David

 

This is not, a new to you car, correct?

 

Good morning Wingrider!
No it is not new to me. My father bought it new and I bought it from him about 8 years ago. It is very low mileage, 30,000 miles and looks brand new. Always garaged. I only use it for special occasions.
By the way I was looking at it last night and I was wrong about the power seats not working, they do work.
Thank you for checking out my post. I would really like to fix it, my father loved this car.
David

 

It sounds like a ground issue. Try a voltmeter and checking the front ground studs to known chassis ground.These lugs will corrode at the chassis and not connect.
I cleaned all I could find fighting air suspension. Even the ones behind the back seat. Never an issue with electrical.
Get a heavy cable and connect one end to the body. Then a VOM to this and check lug resistance to your new ground cable. The lugs should be close to a dead short, zero ohms. At most 1 or 2 ohms. If you find a lug that measures more than a couple ohms this is the problem. Snap off the offender, drill a hole and pit in a brass screw replacement for the aluminum ground lug.
While you are chasing ground measure the resistance of the negative battery cable to body. That should be zero ohms. And you may need a new battery.
I have started replacing them early. No need to stress the charging system propping up a failing battery.
And your environment is perfect for corrosion. High humidity, salt breeze, long periods of non-use. Keep digging this is a cheap fix.

 

Hi Panelhead!
Thanks for your time and advice. I made up a 10 gauge wire and put it on \the battery ground in the trunk. I then went around the car testing the ground lugs. So far they are all 0 ohms. I printed out a diagram of the ground lug locations and will try to find and check them all.
One interesting point is that everything that is not working is controlled by the front electronic module. I am still suspicious of that item, but i will try to check more grounds tomorrow.
Thanks again for your help!
David

 

That is great results. Suspect the lugs on the back of radiator for issues with front control module.you may want to disconnect the battery and then pull plug on the module.
I use Deoxit or another plastic safe contact cleaner. Then smear some dielectric grease on the contacts to protect the connections.
The meter reading are too good. My digital meters and Simpson 260 never show zero ohms when testing grounds. Always show a reading. But four digit digital usually show an ohm or less.

 

Hi again Panelhead!
You are correct that my meters only have 3 digits.
You mentioned lugs on the back of the radiator. Where are they located? I found the lugs on the front of the radiator support and I cleaned then and added a wire from them to the steel bolt that helps support the headlights.
I will disconnect the battery and then remove the plugs from the module. I have some contact cleaner and will use that. I ordered some dielectric grease from Amazon and will use it on the connectors.
Once again thank you for your time and effort on my behalf.
David

 

I just want to thank everyone for the advice, support and willingness to share their excellent technical knowledge!
I checked all of the grounds I could find and cleaned them, also cleaned and applied dielectric grease to the Front control Module connectors. Still no improvement, so I ordered a Front Electronics Module from E-bay and installed it. Voila! For now everything is working as it should! I am very happy!
Once again thanks for all of you generous efforts on my behalf.
I was thinking about the failure of the module. A few months ago the battery died, it was 4 or 5 years old. To get the car going I used the 150 amp boost feature on my battery charger. I replaced the battery and a week or so later had the problem with lights not working etc. Bear in mine I do not use this car very often.
I read in a post somewhere that the boost function on battery chargers can damage the modules. Perhaps that is the root cause of my problem?
I will let you know if it does not stay working.