Cruise control doesn't work

[Barty]

As per the title really. Bought the car a few weeks back knowing the cruise didn't work. Given that it was factory-fitted, I've listed a few things for myself to check. Unfortunately I'm utterly unfamiliar with how the system works, so any pointers to items that frequently go bad related to the CC would be much appreciated

- Clutch sensor (if fitted?)
- Brake sensor (if fitted?)
- Connection at stalk

I don't currently own a suitable code reader (yet), aside from Carly (which is more suitable to coding rather than to diagnostics). I understand this hinders any form of digital diagnostics, so I'll get one in ASAP. Until then, anything worth testing; got nothing to lose by trying! No warning lights or other issues known at this time.

[pvr]

Start at the stalk side, as that is the easy part to see if the cables are ok.

I have only retrofitted one, never actually had one that didn't work though.

[bigwinn]

Barty just a quick check- it’s deffo not working?

I retrofitted one to my first z4 expecting when done to see green lights etc on the dash- it does work but you don’t get any indicators?

Sorry if you are aware of that it just had me confused for a while!

After that I’d go straight to fuses, which will be on the printed card in the fuse box, then pop the steering lower cowling off for a look at the wiring to the plug on the stalk

One other check- do your brake lights come on when braking? Will tell you if the fault is anything to do with the brake switch

[Barty]

Barty just a quick check- it’s deffo not working?

I retrofitted one to my first z4 expecting when done to see green lights etc on the dash- it does work but you don’t get any indicators?

Sorry if you are aware of that it just had me confused for a while!

After that I’d go straight to fuses, which will be on the printed card in the fuse box, then pop the steering lower cowling off for a look at the wiring to the plug on the stalk

One other check- do your brake lights come on when braking? Will tell you if the fault is anything to do with the brake switch

Jep; in the first Z it worked fine: push away to lock speed. Didn't expect any indicators on the dash, but both with a single or double push away the car loses speed (same for a pull on the stalk). Very understandable suggestion, as you'd often expect an indication of some sort to show you you've activated cruise

Good call on the brake switch-check: lights come on just fine so can rule that out.
Fuse box will be the next port of call. Under the bonnet, or is there a second set of fuses in the cabin?

Thanks for the suggestions so far!

[TheDan]

There is a main fuse box in the cabin behind the glovebox. You have to open the glovebox, disconnect the damping tube at the RHS and push the two tabs at the top of the glovebox drawer and it will open all the way down revealing the fuse box.

The fuse for cruise control is fuse 28:

2004 BMW Z4 (E85) Color Fuse Diagram.png (967.14 KiB) Viewed 1021 times

[enuff_zed]

There is a main fuse box in the cabin behind the glovebox. You have to open the glovebox, disconnect the damping tube at the RHS and push the two tabs at the top of the glovebox drawer and it will open all the way down revealing the fuse box.

Is it in the same place on a LHD?
OP is in the Netherlands.

[TheDan]

There is a main fuse box in the cabin behind the glovebox. You have to open the glovebox, disconnect the damping tube at the RHS and push the two tabs at the top of the glovebox drawer and it will open all the way down revealing the fuse box.

Is it in the same place on a LHD?
OP is in the Netherlands.

Ah, didn't see that. As far as I know the interior fuse box is behind the glovebox on all models (EUR, USA and ROW). Just need to reverse my directions for disconnecting the damping tube (LHS of glovebox instead of RHS).

[Barty]

There is a main fuse box in the cabin behind the glovebox. You have to open the glovebox, disconnect the damping tube at the RHS and push the two tabs at the top of the glovebox drawer and it will open all the way down revealing the fuse box.

Is it in the same place on a LHD?
OP is in the Netherlands.

Ah, didn't see that. As far as I know the interior fuse box is behind the glovebox on all models (EUR, USA and ROW). Just need to reverse my directions for disconnecting the damping tube (LHS of glovebox instead of RHS).

Thanks all, will check later today. Judging by that diagram fuse 28 is also responsible for the MFSW (which I don't have) and the rain sensor, which works just fine (plenty of opportunity to test that last week...). I will however take a look, as well as at fuse 14 given that this operates the clutch sensor (tied into CC, I'm sure).

Love the "thiefproofing system" as well; "alarm" wouldn't cover the breadth of their German engineering, no doubt!

[srhutch]

There is a clutch switch and brake switch, either of those could have failed.

Has the ECU had a map though? A mate of mine had the same issue, I re fitted cruise control as the original install (not factory) had been done in a strange way but even wiring correct and replacing the clutch and brake switch we could not resolve. Fuses checked of course. Only conclusion we could come to was the map had removed the cruise function.

[Rockhopper]

When you say it was factory fitted have you checked that with one of the sites that generates the build sheet for your car?

[Barty]

When you say it was factory fitted have you checked that with one of the sites that generates the build sheet for your car?

Good call! I had not, and when I do it doesn’t list it on the options list I was under the impression that the FL always had cruise fitted as standard- clearly not then.

That changes the game, though I do know the stalk has not been fitted recently (seller hasn’t fitted it, so it was there before him).

Back to basics then: check harness, and no doubt you’ll need INPA or similar to code the cruise as “present” into the ECU?

[Rockhopper]

I'm not 100% sure on your car but it might have required an extra loom to be fitted so if the control is actually plugged in then trace the wiring to make sure all the joints are good. On an E85 it'll go though the fire wall and into the ECU.

[Barty]

I'm not 100% sure on your car but it might have required an extra loom to be fitted so if the control is actually plugged in then trace the wiring to make sure all the joints are good. On an E85 it'll go though the fire wall and into the ECU.

Jep, just looked up a diagram on the routing. Once the rain clears I’m going to take a look. Thanks for asking perhaps the most basic question; served as a good reminder not to assume anything

[BumpyZ4]

There is a main fuse box in the cabin behind the glovebox. You have to open the glovebox, disconnect the damping tube at the RHS and push the two tabs at the top of the glovebox drawer and it will open all the way down revealing the fuse box.

Is it in the same place on a LHD?
OP is in the Netherlands.

Yes it is behind the glovebox on LHD cars too.

[Barty]

Never got round to this, so figured an update was well overdue. Checked the fuses, all good.

Today I removed the lower steering column cowel, checking the connectors and stalk

383AA059-2418-454B-9798-D61002260262.jpeg (87.51 KiB) Viewed 766 times

Stalk checks out and seems integrated nicely. However…

8F856460-C885-4A61-8E0D-058D61C5F716.jpeg (54.92 KiB) Viewed 766 times

Two loose plugs. Hhmmm. Any thoughts on these? One purple-yellow and one brown. Is it really as simple as plugging the brown cable into the yellow-purple connector and vice versa? Or would I fry my electrics?

Car electronics aren’t my forte, so apologies for the entirely uninformed question. I much prefer the mechanics over the electrics when it comes to tinkering