Jaguar XJ X350 Adaptive Cruise Repair

Thought I would document my ACC adaptive cruise module fix here in case anyone else is having the same problem. The symptoms are activating cruise gives the message 'CRUISE NOT AVAILABLE' on the dash, and SDD reports a fault with the radar module.

The short version is that the front radar module behind the bumper had water ingress and corroded the main connection terminals. Some careful surgery restored normal service!

Long version:

First job is to remove the bumper cover from the nearside, which covers the ACC module. Insert a large flat-bladed screwdriver into the slot at the top and the cover hinges downwards on 3 prongs and can be removed.

This reveals the radar module. At this point I removed the underside radiator splash shield, and attempted to remove the module from underneath but one of the torx screws holding the module to it's bracket is not accessible without removing more parts. I then decided to remove it complete with bracket from the front. There are two nuts just above the sensor that can be removed with a 10mm spanner. You can then unplug the wiring from the module and remove it. It may be possible to remove the module through the access hole at the front, but as I had the splash shield off I removed it that way.

The bracket then can be removed from the module which is held on with a couple of Torx bolts (think they are T35) and a nut. You can see mine is totally corroded, and clearly something bad has happened looking at the state of whatever it is that's bolted to the side (I think it must be some sort of vent). When shaking the module it sounded like it was full of sand!

Lifting the scanning panel off reveals the motor mechanism. Unscrew the 4 screws in each corner, and gently pull out of the module - it is connected to the base PCB via a multipin plug which will disconnect as you pull the mechanism up and out.

The final board has to be removed, with 5 screws (one of them being on the rusty looking vertical bracket). Be careful here as the main connection socket bolted to the case side has pins which plug into the white connector on the board. Gently lift up the board at the opposite end to the connector and slide out of the pins and lift out.

We can now see what the problem is - two of the pins have completely disintegrated due to corrosion! Luckily the rest of the boards are in good condition.

Both the main connector and the vent on the other side are bolted to the case through their flanges. These would not budge so I used a junior hacksaw to cut the heads off and then prised the flanges off using a flat-bladed screwdriver.

Once the connector and vent are removed, I used a wire brush and wet and dry paper to remove all the corrosion I could from the inside of the case and around the hole for the socket. I also emptied all the loose white dust and brushed this off the boards.

You can see here the damage to the connector and the corrosion around the vent hole

Its clear that I'm not going to be able to re-mount the connector using the bolts and the o-rings have totally failed, so the plan is to repair the pins, remount the socket using sealant, and seal up the vent hole (maybe the vent is needed but nothing I can do about that). The remains of the bolt studs will be used to re-locate the socket into the correct position.

To re-instate the missing two pins on the connector, I used a knife to cut away the plastic around the remains of the pins to get back to good metal - the corrosion was quite deep but luckily managed to expose some copper. 

Then some tinned copper wire needs to be soldered to the copper stumps to create new pins. For this I used the couple of legs of a spare diode I had knocking around as I don't have any lengths of tinned copper wire of the correct diameter.

A bit fiddly but here's the two missing pins soldered back on. A good idea to meter out for continuity at this stage.

Next is to test fit the pins into the socket on the board and test for continuity (meter from the main socket pin on the external side to the pad on the PCB). Not forgetting of course to first extract the remains of the original corroded pins from the white socket. Initially I didn't have continuity on one of my new pins but cleaned up the contact by running another piece of wire in and out of the socket a few times to clean it up.

Time to remount the socket back in the case. I forgot to take a photo of the outside of the case with this in place, but I used some Sikaflex 221 all around the socket and pins, and pushed back into its hole so that the sealant was pushed out, inside and out forming a good seal. Then slid on the inner part of the socket (plastic location pins and plastic sheath around the metal pins) and smoothed out the sealant on both sides to ensure a water tight seal. It doesn't look pretty but its sealed!

Getting the bottom board in is a bit tricky as its a case of trying to engage it with the pins on the connector whilst getting the board in place, but with a bit of jiggery pokery its done. Then simply a case of remounting the motor mechanism and the scanner panel. The plastic cover can then cleaned of old sealant and sealed in place, again with Sikaflex 221. I also sealed up the other hole which I'm still not sure exactly what it's for but think it must be an air-vent or air expansion hole. Hopefully its not essential.

Finished unit:

I left mine a couple of hours for the sealant to harden, then bolted it back on the car. Now, I'm not sure if the next step is necessary but I did it anyway - using SDD tell the system that you are configuring a new ACC module. This will put the module into learning mode which causes the ACC follow light to flash and requires a test drive at over 30 mph to calibrate itself. It doesn't give you any clues as to how long a test drive is required, but after probably about 5-10 miles the light stopped flashing, and I was able to engage cruise control!