[NorcyUK]

Hi guys, I am a new member having recently purchased an E91 LCI 325d M Sport, unfortunately I didn't notice this problem when looking around it before buying

So none of the boot interior lights work when the boot is open. I have tried replacing the bulb in the light fitting on the inside of the boot lid as that bulb wasn't in the best condition anyway, but it obviously isn't a bulb issue when the lights on the left and right hand side of the boot compartment don't work either.

While I was servicing it today, my brother was testing the wiring on the lights and both wires on the connectors were showing 15v, which points to a wiring problem somewhere?

Has anyone else had a similar problem who can guide me in the right direction? I'll be looking at taking it to a trusted auto-electrician soon if I can't solve it myself.

[N5GKP]

Hi Pal,

Do you have the last 7 digits of your chassis number? The three rear interior lights are all supplied from the same area - I've had this fault previously but need to look at a wiring diagram to refresh my memory as it took me a while to work it out before

[Andystobbs]

Does your car warn you that the boot is open?
Is that 15v across the two pins of any light fitting or one pin and chassis ground?

[NorcyUK]

I don't have my chassis number to hand unfortunately.

The wires were tested separately while ground on the boot latch hook.

[Andystobbs]

So you have no ground at the lights. Any abnormal functions of the boot lid?

[N5GKP]

I've created you a PDF of the BMW wiring diagram that shows everything to do with the rear interior / tailgate lighting - It shows the control unit responsible, the fuse number & amperage, how all the lights link, etc.

It's worth noting that 'A4010' is the Junction box fuse board, whilst 'A4010a' is the Junction Box Electronics control unit which attaches to the fuse board.
Both located behind the glove box.

The lights on these are switched by either the central locking drive on the boot lid, or the rear window latch. So you'd expect to see voltage right up to 'X311' on M17a & 'X13059' on M96a - Which are both the connectors at the tailgate lock + the rear glass hatch lock.

I hope this is of some help?

[NorcyUK]

Originally Posted by Andystobbs

So you have no ground at the lights. Any abnormal functions of the boot lid?

Only thing I have noticed after the first time I used the boot was the 'Open Boot' warning, but I was putting that down to my stiff boot hinges I've used the boot several times since and not had the warning again.

[NorcyUK]

Originally Posted by N5GKP

I've created you a PDF of the BMW wiring diagram that shows everything to do with the rear interior / tailgate lighting - It shows the control unit responsible, the fuse number & amperage, how all the lights link, etc.

It's worth noting that 'A4010' is the Junction box fuse board, whilst 'A4010a' is the Junction Box Electronics control unit which attaches to the fuse board.
Both located behind the glove box.

The lights on these are switched by either the central locking drive on the boot lid, or the rear window latch. So you'd expect to see voltage right up to 'X311' on M17a & 'X13059' on M96a - Which are both the connectors at the tailgate lock + the rear glass hatch lock.

I hope this is of some help?

That's some great information, thank you, I'll have to study it a bit further when I get chance. Am I right in thinking that fuse no. 61 is for the boot compartment lights? As that didn't have a fuse in it when I was looking yesterday. I put one in but this made no change.

[N5GKP]

Fuse 61 is the supply correct. As the 'switches' are below the consumer (lights) the voltage will be present across the lights, all the way to the switches which can cause a bit of confusion with diagnosis.

[NorcyUK]

Originally Posted by N5GKP

Fuse 61 is the supply correct. As the 'switches' are below the consumer (lights) the voltage will be present across the lights, all the way to the switches which can cause a bit of confusion with diagnosis.

So the 15v shown on both wires in the light connectors aren't a sign of a problem because they are switched at the boot latch? The fuse box cover at the back of the glovebox was loose and just sat in the glovebox when I first opened it, so I'm assuming there's been some fiddling around in there at some point

[N5GKP]

If you have a look at the modified PDF i've attached this time, I've added some thick pink lines in, I'd expect to see battery voltage along those lines right until they stop at the bottom (when comparing the lines to earth as multimeters measure potential difference).
If the glovebox light works - chances are it's not a fuse / junction box or junction box electronics fault. Equally, pull the fuse and i'd expect the glove box light to stop working + no voltage to be present where you've previously measured voltage.

You may then be looking at an issue with your tailgate wiring harness where it runs through the hinges, or an internal fault within the rotary switch in the tailgate latch.
Have you tried opening the glass hatch to see if that turns the interior lighting on?

[Tambohamilton]

Following this thread as I also have some funny business going on with my e91 tailgate. My problem is that it never locks/can always be opened...everything else seems to work absolutely fine.

[Andystobbs]

Bound to be broken wires in the harness. Probably in both cases.

[Tambohamilton]

True. I've got a repair harness waiting to go into mine when I have the time. However everything that I've tested on mine so far has checked out; continuity to the correct pins between the tailgate latch plug and JBBF, correct operation of the switches in the latch, correct interior light function...all seems fine! I'll report back when I get around to replacing the wiring at the hinge. Here's the thread on mine, which also has useful information on wiring and diagnostics from others:
https://www.e90post.com/forums/showthread.php?t=1662097

[Andystobbs]

Yeah yours is interesting given that the boot lock isn't really a locked or unlocked set up. Its only ever a release when allowed by the car.

[Tambohamilton]

Yep, it's a "fun" one... That's why I'm doing nothing more on it until I've made sure the wires are all good.

Back on topic though, I think it'll be a good idea for the OP to check his wiring in the tailgate hinge grommets...even if it doesn't end up being the problem.

[NorcyUK]

Yeah I think I need to check the wiring in the hinges, the glovebox light is working fine, so it has to be an issue further along the line.

Where did you get the repair harness from?

[Tambohamilton]

I got mine from autodoc (same as buycarparts and a few others). Watch their prices - they change daily, if not hourly. Don't just watch the discount, because the base price changes too.

There are a few available, so find all info you can about the number of wires, their thicknesses, etc.

A genuine BMW part is £400ish, I think. I paid £100ish for mine, which still seems steep for a handful of silicone insulated wires, connectors, a rubber boot, and some washer hose. I was just going to buy some lengths of wire and connectors, but then I noticed a small hole in the rubber boot - that was enough to tip the balance for me!

[NorcyUK]

So then, I apologise for not writing on this post for a few weeks, but I got distracted with the build up to Christmas, followed by being ill over Christmas as well! Amongst all that I suddenly realised one evening when opening the glass boot hatch that the interior boot lights come on when that is open on its own, but not when the full boot lid is opened.

[Igor_M5]

Originally Posted by Tambohamilton

Following this thread as I also have some funny business going on with my e91 tailgate. My problem is that it never locks/can always be opened...everything else seems to work absolutely fine.

Had this issue on my 06 E91, ended up just needing to replace the latch on the tailgate.

[Tambohamilton]

Good to know, thanks! I've only found one other person with the problem so far, and they replaced the latch and switch to no avail... Anyhow, I'll sort my wiring first, and then see where I'm at.