Cruise Control Stopped Working in 5th and 6th Gears Only

radicalmachine · Post by **radicalmachine** » Mon Jun 15, 2020 9:35 am

Hi Chaps,

Odd one for you. Factory-fitted cruise control on my 2010 E89 has always worked no issues, until now:

Cruise control works absolutely fine above 20mph in gears 1-4, but for no apparent reason not in 5th and 6th gears. If cruise control is engaged in 4th gear and I change to 5th, it disengages with the yellow cruise control warning light (indicating pre-conditions for cruise control are not met). If I try to engage cruise control while in 5th or 6th, I get the three-dashes (---mph) instead of the speed.

Scratching my head on this one, as I'm not getting the cruise control malfunction light, and works no problem in other gears. There are no fault codes in the ECU to indicate any issues.

Anyone seen this before?

enuff_zed · Post by **enuff_zed** » Mon Jun 15, 2020 10:48 am

This is only a wild stab, but is it maybe thinking the revs are too low?
Does it measure that?
I don't know, just saw a straw blowing by and clutched at it.

Beeacon · Post by **Beeacon** » Mon Jun 15, 2020 11:14 am

This is very strange. On mine it won't let me do cruise control in sport+ mode but that's it other than below 20mph.

clarker63 · Post by **clarker63** » Mon Jun 15, 2020 1:11 pm

radicalmachine wrote: ↑Mon Jun 15, 2020 9:35 am Hi Chaps,
Anyone seen this before?

Are you on stock tyres/wheels?

Just a comment on another forum with a similar issue.. although they had retrofitted cruise and it needed some additional coding...

https://www.bimmerfest.com/forums/archi ... 35478.html

R.E92 · Post by **R.E92** » Mon Jun 15, 2020 7:46 pm

I was thinking it could be down to wheels and tyres too. Having wheels with a larger rolling radius will cause cruise control issues, people often have this problem when changing the final drive ratio on their car, cruise will stop working in higher gears.

radicalmachine · Post by **radicalmachine** » Mon Jun 15, 2020 10:41 pm

Thanks for the thoughts chaps.
She sports genuine BMW 19inch V-Spoke 296 wheels with Goodyear Eagle F1 Asymmetrics all-round, so I suspect that's not the issue. I've just taken ISTA-D outside on the laptop to make sure I'm not going mad, and there is a single fault code 'A6A2 Soft Close Automatic' in the CTM module (so clearly an issue for another day

).

Taken her out for a spin and sure enough cruise control engages no problem up to 4th, and disengages in 5th / 6th. Nothing has recently changed on the car except a new battery but if anything I would have thought that would nix the entire system not just in 5th and 6th gear.

Proper head scratcher!!

mcbutler · Post by **mcbutler** » Wed Jun 17, 2020 1:10 pm

Beeacon wrote: ↑Mon Jun 15, 2020 11:14 am This is very strange. On mine it won't let me do cruise control in sport+ mode but that's it other than below 20mph.

Normal, my 35i is the same

mcbutler · Post by **mcbutler** » Wed Jun 17, 2020 1:13 pm

Your changing up a gear when you are going to slow, the car recognises this and wont allow you to use cruise as revs are too low. If you go 5 mph or so faster I am sure it'll be fine.
It'll do this on hills as well if the revs are too low.

Nictrix · Post by **Nictrix** » Wed Jun 17, 2020 2:39 pm

Are you putting it in 6th and then engaging cruise or engaging cruise and then changing gears?

ph001 · Post by **ph001** » Wed Jun 17, 2020 2:41 pm

Hmmm it's an odd one. Could your clutch be worn at all (check by putting into top gear, holding the brake lightly and trying to accelerate) if the revs rise with no speed increase yo have a slipping clutch.

Other than that I can only think of a DSC control unit problem

radicalmachine · Post by **radicalmachine** » Wed Jun 17, 2020 7:20 pm

All good suggestions chaps:

mcbutler wrote: ↑Wed Jun 17, 2020 1:13 pm Your changing up a gear when you are going to slow, the car recognises this and wont allow you to use cruise as revs are too low. If you go 5 mph or so faster I am sure it'll be fine.
It'll do this on hills as well if the revs are too low.

Doesn't matter how low or high the revs are or how slow or fast I'm going, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

Nictrix wrote: ↑Wed Jun 17, 2020 2:39 pm Are you putting it in 6th and then engaging cruise or engaging cruise and then changing gears?

Both, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

ph001 wrote: ↑Wed Jun 17, 2020 2:41 pm Hmmm it's an odd one. Could your clutch be worn at all (check by putting into top gear, holding the brake lightly and trying to accelerate) if the revs rise with no speed increase yo have a slipping clutch.

Other than that I can only think of a DSC control unit problem

Tried this just now and no slippage, clutch holds well.

I thought it could perhaps be related to tyre pressure, so topped the air up to 2.4bar in front and 2.9 bar in rear as recommended on the vehicle, but no dice there either. I guess the last thing I can try is get familiar with NCSExpert and check that cruise-control is coded correctly as per Clarker63's suggestion, though cruise was factory-fitted so I feel this has a slim chance of yeilding results.

Keep 'em coming boys

Smartbear · Post by **Smartbear** » Wed Jun 17, 2020 7:32 pm

radicalmachine wrote: ↑Wed Jun 17, 2020 7:20 pm All good suggestions chaps:

mcbutler wrote: ↑Wed Jun 17, 2020 1:13 pm Your changing up a gear when you are going to slow, the car recognises this and wont allow you to use cruise as revs are too low. If you go 5 mph or so faster I am sure it'll be fine.
It'll do this on hills as well if the revs are too low.
Doesn't matter how low or high the revs are or how slow or fast I'm going, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

Nictrix wrote: ↑Wed Jun 17, 2020 2:39 pm Are you putting it in 6th and then engaging cruise or engaging cruise and then changing gears?
Both, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

ph001 wrote: ↑Wed Jun 17, 2020 2:41 pm Hmmm it's an odd one. Could your clutch be worn at all (check by putting into top gear, holding the brake lightly and trying to accelerate) if the revs rise with no speed increase yo have a slipping clutch.

Other than that I can only think of a DSC control unit problem
Tried this just now and no slippage, clutch holds well.

I thought it could perhaps be related to tyre pressure, so topped the air up to 2.4bar in front and 2.9 bar in rear as recommended on the vehicle, but no dice there either. I guess the last thing I can try is get familiar with NCSExpert and check that cruise-control is coded correctly as per Clarker63's suggestion, though cruise was factory-fitted so I feel this has a slim chance of yeilding results.

Keep 'em coming boys

You could try a battery disconnect to see if it resets the problem.
Rob

Pbondar · Post by **Pbondar** » Wed Jun 17, 2020 8:16 pm

Smartbear wrote: ↑Wed Jun 17, 2020 7:32 pm
radicalmachine wrote: ↑Wed Jun 17, 2020 7:20 pm All good suggestions chaps:

mcbutler wrote: ↑Wed Jun 17, 2020 1:13 pm Your changing up a gear when you are going to slow, the car recognises this and wont allow you to use cruise as revs are too low. If you go 5 mph or so faster I am sure it'll be fine.
It'll do this on hills as well if the revs are too low.
Doesn't matter how low or high the revs are or how slow or fast I'm going, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

Nictrix wrote: ↑Wed Jun 17, 2020 2:39 pm Are you putting it in 6th and then engaging cruise or engaging cruise and then changing gears?
Both, cruise control gives me '---mph' when attempting to set while in 5th or 6th, or displays the 'cruise-control pre-conditions not met' symbol when changing up from 4th to 5th.

ph001 wrote: ↑Wed Jun 17, 2020 2:41 pm Hmmm it's an odd one. Could your clutch be worn at all (check by putting into top gear, holding the brake lightly and trying to accelerate) if the revs rise with no speed increase yo have a slipping clutch.

Other than that I can only think of a DSC control unit problem
Tried this just now and no slippage, clutch holds well.

I thought it could perhaps be related to tyre pressure, so topped the air up to 2.4bar in front and 2.9 bar in rear as recommended on the vehicle, but no dice there either. I guess the last thing I can try is get familiar with NCSExpert and check that cruise-control is coded correctly as per Clarker63's suggestion, though cruise was factory-fitted so I feel this has a slim chance of yeilding results.

Keep 'em coming boys
You could try a battery disconnect to see if it resets the problem.
Rob

SmartBear May be on to something..the E89 is notorious for spurious issues created by battery / supply related issues.

I would suggest..

Disconnect battery..wait 60 minutes

Reconnect and re-register , did you change capacity? If so update status..

Then try again..

Grasping at straws but in these situations with no other diagnostics ..did you use a code reader in the first place?

mcbutler · Post by **mcbutler** » Wed Jun 17, 2020 10:36 pm

The question is what is different between a set rpm in 1-2-3-4 and it working to the same RPM in 5-6 and it not working!!
Have you tried in sport as well as comfort?
I think as forum members/owners and not techncians solving this, you may have to bite the bullet and take it to your indy, might be worth calling a few garages and asking for advice, never hurts to try.

enuff_zed · Post by **enuff_zed** » Thu Jun 18, 2020 8:06 am

Another wild stab at it from me:

The '---mph' kind of suggests it doesn't know what the speed is.
How does the Z4 get it's speed reading?
Is it off the gearbox?
Is it possible that there is a problem with a speed sensor?

Now I'm second guessing myself and wondering if that would mean the speedo not registering either?

Z4-forum.com

Z4-forum.com