How-to retrofit the 'BMW square box' type ultrasonic volumetric interior alarm sensor

[Bolin]

This How-to describes how I fitted the later 'BMW square box' type interior ultrasonic volumetric alarm sensor. This procedure should the same for all models. You may wish to do it in a slightly different way, but the general procedure will be the same.

The later 'BMW square box' type sensor was fitted to cars from VIN 171486 onwards. Cars up to VIN 171485 were fitted with the earlier 'Rover toblerone' type sensor. The difference between the two is that the 'Rover toblerone' type sensor is made up of two actual sensors and is fitted above the B pillar on the driver's side (UK cars, export cars may be different) whereas the 'BMW square box' type is made up of four actual sensors and is fitted in the centre of the headlining.

The 'BMW square box' sensor set-up consists of:
The sensor itself, made up of four ultrasonic sensors integrated into one unit
Top mounting 'sandwich' plate
Bottom mounting 'sandwich' plate
Exterior cover with fabric glued on and two small grilles
Wiring loom, integrated with the rest of the headlining wiring loom.

Note: When handling the cover, be careful not to damage the two pieces of felt-like material on the inside of the two grilles. Mine looked a bit dusty, so I tried to rub the dust off, only to find the material turned into fluff with no effort at all! I had to source some more from another cover.

Here is picture of the bits that I purchased, note that I had only a partial wiring loom:



The sensor, two roof mounting 'sandwich' plates and cover appear to be the same as those used on the BMW E38 (7 series 94-01), E39 (5 series 95-02) and E46 (3 series 98-05) although I cannot guarantee what years this sensor was used exactly, they are are plentiful and fairly cheap on eBay. I cannot vouch for the colour match of the cover fitted to BMWs in comparison to the interior of our cars, but can say that the plastic underneath the glued-on fabric covering is a BMW moulding. The covers used on BMWs also came in black, light grey (lighter than Rover's Light Smokestone) and a darker beige (closer to tan) than Rover's Sandstone Beige and some were also rectangular for no apparent reason – all the fixing are absolutely identical and the rectangular type will also fit the 75/ZT.

Getting hold of the wiring for the sensor is the tricky bit, perhaps because it is integrated with the headlining loom, which is itself glued to the top of the headlining. I haven't seen any of the wiring for sale, either from BMWs or 75/ZTs, but the wiring terminals are the same as those used for wiring powerfolds and many other parts of the car's body electrics, and can be obtained from here: http://uk.farnell.com/te-connectivit...-in/dp/1330225 and also from eBay. The terminals are the female type, and are used on both ends of the loom – at the sensor end and the end that goes into the largest multi-plug connector at the base of the A-pillar (C0610). The sensor loom has a plastic connector where it connects to the sensor unit, with four positions – this may possibly be used elsewhere on the car but I do not know.

To start the retrofit, begin with the wiring so that it is all ready to install when you have cut the hole and lowered the headlining.

The wiring goes like this:

The sensor has four wires coming from it - 2 black (earth), 1 pink/green (trigger) and 1 pink/yellow (+12v power).

The 2 black wires go from pins 1 and 2 in the sensor and merge before the A-pillar connector. The then single black wire merges with the black wire in the existing headlining loom that goes to pin 3 in the main connector block at the base of the A-pillar. Alternatively, the two black wires may merge at the same time as joining the existing black wire in the headlining loom, or all three could even be crimped together with the terminal that goes into the connector block- it shouldn't matter either way, but the latter two methods will require more wire.

The pink/green wire goes from pin 3 in the sensor to pin 5 in the main headlining connector block.

The pink/yellow wire goes from pin 4 in the sensor to pin 4 in the main headlining connector block.

The pin numbers are indicated on the sensor, plastic connector and the A-pillar connector; look carefully and you will see them.

My car had the wiring present from the BCU to the A-pillar connector, but it appears that not all cars have this present. If not, then you may need to extend the pink/green wire to pin 31 on connector C0660 on the BCU (the middle connector) and the pink/yellow wire to pin 15, also on connector C0660 on the BCU.

It is worth noting that later cars, built from January 2003 with the later wiring loom MAY NOT have the wiring in the car going from the BCU to the A-pillar connector block. I say this because these cars didn't have the powerfold wiring from one door to the other in place, I believe, and wiring for many other optional items was also removed. It should be possible to add this wiring if it is missing, but it may be best to check your car before purchasing parts!

To check if the wiring is present from the BCU to the A-pillar connector, look to see if pins 4 and 5 in the A-pillar connector are populated with terminals. You will need to remove the A-pillar trim to access this connector; to do this on a car without ITS head airbags just pull away the trim from the top until three clips disengage, then stick a thin screwdriver or similar between the trim and the dashboard near the front, by the windscreen, to release a clip and then pull the trim upwards. The procedure for cars with ITS head airbags may be different, I do not know.

The length of the wiring from the sensor to the A-pillar connector is a bit under 290cm following the OEM routing – if you use this length it will leave plenty of slack depending on the exactly how closely you follow the original wiring and there will be some excess at the A-pillar connector end. It is better to have the wiring too long, as it can be shortened to suit before fitting the end terminals for the A-pillar connector block, rather than being too short, which could be a pain to sort out.

To make up the required loom, measure out 290cm of 5 amp wire and crimp on one terminal at one end, which will become the sensor end (I used a special crimping tool, there may be other tools that can crimp the terminals on, I do not know). If you already have some wiring, like I did, you can just solder on some extra wire to make up the required length. Repeat this for each one of the three different wiring colours.

Do the second earth by also adding a terminal to this wire and running it from the sensor end of your loom with to a distance of at least 5cm and not more than about 270cm (to be safe in the case of there being a lot of excess left over), if you intend to follow the OEM routing. If you wish to take a different route, presumably shorter, then ensure that the second earth is joined somewhere before the A-pillar connector. Cut the existing earth wire, strip both cut ends and that of the second earth, twist and solder together to form a junction. Alternatively, if you wish to run the second earth to the terminal in the connector block, then repeat the procedure in the above paragraph, so to match what you have done for the other wires.

It would actually be possible to merge the two earth wires, from the sensor, into the headlining loom at any point between where the sensor loom routing joins into the existing headlining loom routing (which is at a position parallel to the sensor but at the right side of the headlining) and the connector block at the base of the A-pillar. However, I preferred to have an earth wire going down all the way to the connector block because it is easier to work on the existing headlining loom down near the connector block as otherwise you have to work on the loom stuck to the top of the headlining, whilst the headlining is lowered down and not firmly held steady! Also access space would be more restricted in such a position.

Here is a picture of the joins where I extended my loom, also where I merged the two earth wires coming from the sensor – I finished them off with some heat shrink sleeve.



If you have made the loom from scratch, you can fit the plastic connector for the sensor end if you have it, ensuring the wires are in the correct pin locations. If the wires you have used/added are not the correct colours, then add labels with the correct colours and pin locations at the A-pillar connector end of the loom, and to the sensor end too if you don't have the plastic connector, to aid identification once the loom is in position. Bind the wires together at various points along the loom to make it easier to handle.

It's now time to start marking out the position of the hole that needs to be made in the headlining. The rearmost edge of the sensor cover is located 310mm forward of the front edge of the rear interior lamp. As the cover is 142mm long, 71mm needs to be added to the dimension above to locate the centre of the hole, which therefore needs to be 381mm forwards of the rear interior lamp.

To get the position of the centre of the hole in the middle of the headlining rather than off to one side, I ran a tape measure across the headlining from the middle of the front-most edge of the rear lamp to the middle of the back edge of the front lamp. I think I had to use my foot to hold the tape in place all the way to the front lamp, this will be easier if you can convince an assistant to help!



Mark a dot at 381mm.



Then measure out from the dot to a point on each of the rear grab handles, and check that this measurement is same either side, so to ensure that the dot is in the centre of the headlining. If it isn't, try to correct it and check again.

As can be ascertained from the fixings on the sensor cover, the hole needs to be 100mm long and 108mm wide. Put the tape back up again from between the middle of the front-most edge of the rear interior lamp to the dot you have made. Keeping it straight, mark dots at 331mm and 431mm for the front and rear ends of the hole.



Again, measure out from these dots to a point on each of the rear grab handles, and check that this measurement is the same for both sides for each dot, so to check that the dots are in the centre of the headlining. If the measurement differs, try to correct the dots and check again. Then join the three dots with a line to make a 'length line'. Check that the three dots lay on the line, if not correct and check again.



Using a protractor, make a mark at 90 degrees from the centre of the existing line on both sides.





Join these with a line 108mm long, ensuring that the middle of the line (at 54mm) crosses the 'length line', as this will mark out the width of the hole ('width line'). The dots on each side, mentioned above, along with the first dot made in the centre, should all lay on the line. If not, make corrections and check again.



Measure out from the ends of this line to a point on the nearest rear grab handle, and check that this measurement is same either side, so to check the line is straight across the width of the headlining, and not skewed. If it isn't, try to correct it and check again.

Use the protractor at the ends of the 'width line' at 90 degrees to mark the position of the four corners – my protractor was 50mm from the 'eye' to the edge, ideal as this is the dimension required at these points.





Check the position of the corner points by measuring from them to the ends of the 'length line', this measurement should be 54mm, being half of the width of the hole. Then measure out from these latest dots to a point on the nearest rear grab handle, and check that the measurement for the front-most dots is the same and then that for the rearmost dots is the same. If not, correct and check again.



Then join the latest dots together, to make a square, checking that the ends of the 'width line' and 'length line' finish at the middle of the new lines. If not, correct and check again.



You then need to mark a cut out for a locating 'spike' that is on the top mounting 'sandwich' plate. 20mm towards the rear from the middle of the right side of the square, mark a dot 2.5mm towards the right side of the car and draw a 5mm square around it. This can be done without further measuring and checks as it is not critical for getting the sensor in the correct position.



Now it is time to cut out what you have drawn.

CAUTION: The backing of the headlining appears to contain some nasty fibres that irritated my skin when I previously removed it and swapped it for a different one. I am not allergic to anything, so there must be something really quite nasty in the backing. I suggest that you wear gloves for the nest steps (and goggles too whilst cutting the hole), until the headlining has been refitted and the interior has been vacuumed. You may also want to lay some sheeting over the interior as an additional precaution.

To start making the hole I used a drill, as I think to have tried to puncture the headlining using another method may have caused it to crease over a large area due to the pressure required. Be careful not to overshoot with the drill or you may end up with a hole in your roof! I used the biggest drill bit I had and drilled three holes close together so to easily break between them and get some beefy scissors in there.







Gradually cut out the hole that you have marked.





It's now time to lower the headlining. Remove the A-pillar trims as previously mentioned, and unclip the wiring now exposed. Unclip and pull off the D-pillar trims, unclip the combined B-pillar trim from the bottom upwards and pull it down, and then remove the grab handles, sunvisors and front interior lamp. Slide the headlining forwards and then pull it downwards, and move the front seats and adjust the head restraints to support it in a lowered position.

Fit the top mounting 'sandwich' plate from the top side of the headlining, ensuring the 'spike' is located in it's hole.



From underneath, loosely clip in the bottom mounting 'sandwich' plate, ensuring the 'spike' from the top plate fits through the hole in the bottom plate.



Now fit the loom in place. Tape it from the sensor hole, leaving a good 10cm or so at the sensor end of the loom hanging through the hole so to give enough slack to fit the sensor and manoeuvre it into the cover. Tape the loom towards the existing loom on the right side of the headlining and then follow the existing loom around, taping it down at various points. If you want to take a different route with the loom, it should be possible, especially as the OEM route does double back quite a bit around the area of the sunvisors. Note that my photos show tape holding down the existing loom, this is because I had previously swapped my headlining but kept the original wiring. The existing loom should be glued in place.





Also tape the sensor loom to the existing loom where it is loose between the front right corner of the headlining and the connector at the base of the A-pillar.

Now it is time to finish off the wiring. Cut the pink/yellow and pink/green wires to the required length to removing any excess, and crimp on the terminals. Plug the pink/yellow wire into pin 4 and the pink/green wire into pin 5.

Remove pin 3 with the existing black wire, cut it, strip the ends, and then cut the black wire(s) in the sensor loom as required, strip the end, twist it into the existing black wire and solder them together. Alternatively, you may wish to try removing the terminal and simply crimping the black wire(s) from the sensor and the existing headlining loom together with a new terminal. Below is mine, but with the other wires not yet plugged in.



Plug the combined black wire back into pin 3, as well as the others if not done yet.



Refit the headlining, for the rear clips push them firmly up into the locating holes, and slide the headlining as far back as it will go. Clip the wiring in place down the A-pillar. Fit the other bits removed previously; the A-pillar trims (for cars without ITS head airbags at least) do not need the clip near the windscreen to be held with a screwdriver, they just push down and in. Run the door seal edges over the edges of the headlining and trim panels. Vacuum the interior to remove any potential nasty fibres that may have been released by the headlining.

Tightly squeeze up the mounting plates for the sensor. I found that there was a bit of slack in the hole, possibly because it was hard to cut the hole accurately using scissors. If you find this too then adjust the position of the mounting plates by wiggling them and then measure out from the corners of the bottom plate to a point on the nearest rear grab handle, and check that the measurement for the front-most corners is the same and then that for the rearmost corners is the same. If not, wiggle the mounting plates and check again.

Now clip the wiring into the sensor, taking care to use the correct pins if you don't have the plastic connector (it may also be a good idea to cover the bare terminals with insulating wire in this situation), clip the sensor into the cover (ensuring that the arrow on the inside of the cover is pointing towards the front of the car) and clip the cover into the mounting plates, ensuring you hear each of the four corners 'click' into place.







You can test the function of the sensor at this point. To test, sit inside the car and lock with the remote. After 20 seconds start waving your arms about and move your torso, this should set off the alarm. Mine worked without having the car's ZCS codes changed with a T4. The 20 second delay is built into the system, to allow the air in the car to settle down so to prevent inadvertent activation of the alarm.

You should then get the ZCS codes updated to complete the electrical side of things. I presume that doing this will enable the car to perform diagnostic checks on the sensor unit. You will need to see one of the known T4 gurus for this, i.e. BigRuss (who did mine), MarinaBrian, Phil-T4, Monk etc.

Now you can be assured that the interior of your car is better protected in the case of break-in, as the alarm will hopefully scare off any miscreants before they can steal anything and it should also alert those nearby.


Disclaimer:
You are responsible for any work or modifications carried out on your car and you undertake any such work at your own risk. Neither the 75 and ZT Owners Club nor the original authors in this thread can be held liable for anything that may happen as a result of you following this guide.
Any modifications should be reported to your insurance company.

[Bolin]

Well that took bloomin' ages to write all that!

Sorry about the last two pics, can't seem to rotate them now they are uploaded.

It isn't as hard as the length of the How-to would have you beleive, I'm just very good at saying as little as possible in the most number of words!

[Reebs]

Fantastic work Colin, and it must have been a breath holding moment when you attacked the roof lining with the drill

I have copied the How To into the 'How To - Car Interior forum for future reference. Many thanks

How-to retrofit the 'BMW square box' type ultrasonic volumetric interior alarm sensor

[Bolin]

Many thanks for the kind words Paul, yes I was a bit nervous when using the drill, after all an extra hole there would not have been desired to put it mildly!!

Thanks for putting it into a How-to, if anybody spots any errors or amendments to be made then I will ask for these to be put into the other forum too.

[phenonix]

Well done Colin!
I'd like to check my BCU has the connections before pulling away the A pillar (as i have air bags and i've heard once the covers are removed it is advised to fit new ones)

Can you remind me what pins need to be populated in the BCU so i can see if i have them?

Do you think i could do this upgrade without dropping the headliner?, i mean maybe using a coat hanger to run the loom to the front?

I'm also thinking of avoiding the A pillar connector (for the reasons above) and maybe just going direct to the BCU, or taping into the wire that run from the BCU which i'm guessing would be under the steering column

I'm going to have to make the loom form scratch although i do have those tiny crimps from upgrading to powerfolds.

[Bolin]

Originally Posted by phenonix

Well done Colin!
I'd like to check my BCU has the connections before pulling away the A pillar (as i have air bags and i've heard once the covers are removed it is advised to fit new ones)

Can you remind me what pins need to be populated in the BCU so i can see if i have them?

Do you think i could do this upgrade without dropping the headliner?, i mean maybe using a coat hanger to run the loom to the front?

I'm also thinking of avoiding the A pillar connector (for the reasons above) and maybe just going direct to the BCU, or taping into the wire that run from the BCU which i'm guessing would be under the steering column

I'm going to have to make the loom form scratch although i do have those tiny crimps from upgrading to powerfolds.

Thank you!

I honestly don't think it can be done without dropping the headlining as there is not enough space to get the top mounting plate in. However, you might be able to drop just the rear of the headlining (remove D-pillar trims and pull down to disengage the 2 clips in the headlining itself), and feed the mounting plate across from there, or perhaps even through the hole for the front interior lamp - not sure the plate will fit through the hole though. The loom could be feed down the D-pillar and along the carpet perhaps?

As for the BCU wiring, it should be accessible under the dash to tap into. I'll have a search on here, I think the wires to the BCU are described in an old thread.

[phenonix]

I forgot about getting that plate in , i was only thinking of the wires.

I also cannot go through the front light switch as i have a sun roof.

After the success of getting that impossible screw fitted for my reverse sensors i'd like to give it a try without dropping the head lining!

magnet won't work this time

[Bolin]

Well dropping the headlining at the back would appear to be the only possibility then.

I have found info about the BCU wiring, actually posted by yourself and Reebs a few years ago:

http://www.the75andztclub.co.uk/foru...t=45410&page=3

[phenonix]

Thanks, never sure if it was correct.

[carl_z_t]

sorry to bring up a old thread, but im half way thru doing this but my wire colours are different, I still followed the pin 1 2 on the sensor to earth and the others to 4 and 5, but it doesnt work at all, any idea what way round these wires should be?I got a brown with a black stripe on pin 1, black with a red stripe on 2, black with a yellow stripe on 3 and a red with a black stripe on 4, its the same sensor, just different wiring for some reason?