Z4M Limp Mode

[zomby]

Hi all. Been having some issues recently with my Z4M randomly going into limp mode, and the usual EML, ABS and DSC warning lights flash up. It seems to happen pretty randomly when I'm driving along, and when it does, the throttle becomes very jerky. If I disconnect and reconnect the battery, the warning lights clear and I'm able to drive normally again but the issue will reoccur every 50-100 miles or so. The car drives absolutely fine when it's not on limp mode; I don't notice any loss of power and MPG is where I'd expect it to be.

Before getting the codes read I thought it might've been the throttle position sensor so I ordered a new one and replaced it (the easily accessible one, which did look a little worse for wear). The issue's not occurred since then, but then again I've not driven it too far.

I've since hooked the car up to INPA which has revealed the following codes (translated):
Error: 1(6) No.: 12160 2F80 Engine shutdown time, plausibility Frequency: 1
Error: 2(6) No.: 11552 2D20 Accelerator pedal module, pedal value transmitter, plausibility between signal 1 and signal 2 Frequency: 1
Error: 3(6) No.: 11612 2D5C DME, internal error: Monitoring Hardware Frequency: 1
Error: 4(6) No.: 11730 2DD2 Message from LWS control unit missing, LWS frequency: 1
Error: 5(6) No: 11724 2DCC message from ASC/DSC missing, ASC 1 Frequency: 1
Error: 6(6) No: 11725 2DCD message from ASC/DSC missing, ASC 3 Frequency: 1

Looking at those errors, I'd guess that going by the symptoms that it's the accelerator pedal module that's the root cause of the issue and causing all the others to come up. It looks to be a fairly cheap and easy part to replace so I'll probably start with that unless anyone has any other ideas? I'll then clear the codes and see whether anything comes up again.

Thanks in advance

Full error code extract can be seen here:
https://docs.google.com/document/d/1_FaTzU2lwt6BbioCcFcy8_KnXfPwbP_pRdiqkE7GUDo/edit?usp=sharing

 

[AndyBeech]

I would say clear the codes and go again, lot going on there to narrow it down tbh. Trouble with that many fault codes you don't know which one is setting off the other, ie. hard to narrow down what the actual issue is.
I would say very rare for the throttle pedal itself to fail or be an issue although not impossible I guess. The one underneath the airbox attached to the actuator is far more likely.
Any battery issues you know of? As always a tired battery can cause weird and wonderful things to happen....

Your google docs link is locked btw.

 

[j3nks79]

Throttle position sensor on the accelerator is the problem

 

[tomscott]

Is your battery healthy? A low battery can start playing havoc

 

[LawrenceW]

Can i jump in with a quick question on battery replacement - I plan to replace my battery on my Z4MC given the current one is 8 yrs old. Is it simply a case of old one out/new one in? or is there any coding requirements i.e. stereo? keys etc? Thanks

 

[Zedebee]

The only time I have had this problem (on a non-M), it turned out the battery connection was simply not tightened down correctly. It seemed OK, but jaws obviously disconnecting intermittently when driving along. Cleaning the terminal and making sure the connector was properly tightened down sorted the problem.

Easy and cheap thing to check before you do any more head-scratching.

 

[zomby]

I would say clear the codes and go again, lot going on there to narrow it down tbh. Trouble with that many fault codes you don't know which one is setting off the other, ie. hard to narrow down what the actual issue is.
I would say very rare for the throttle pedal itself to fail or be an issue although not impossible I guess. The one underneath the airbox attached to the actuator is far more likely.
Any battery issues you know of? As always a tired battery can cause weird and wonderful things to happen....

Your google docs link is locked btw.

Apologies - google doc is now unlocked. So do you mean the throttle position sensor that's under the airbox? I thought the TPS would have their own error codes hence why I thought my original diagnosis was incorrect. If the issue reoccurs I can always swap the new one I just fitted with the one underneath the airbox and put the old one back.

I'm pretty positive it's not battery related. I replaced it a few years ago with a Varta and since then it's always been hooked up to a ctek all year round.

Can i jump in with a quick question on battery replacement - I plan to replace my battery on my Z4MC given the current one is 8 yrs old. Is it simply a case of old one out/new one in? or is there any coding requirements i.e. stereo? keys etc? Thanks

Yes it was just a plug and play for me, no coding required.

The only time I have had this problem (on a non-M), it turned out the battery connection was simply not tightened down correctly. It seemed OK, but jaws obviously disconnecting intermittently when driving along. Cleaning the terminal and making sure the connector was properly tightened down sorted the problem.

Easy and cheap thing to check before you do any more head-scratching.

I'll definitely give this ago. I do end up disconnecting the negative terminal quite often in order to get the car out of limp mode but I thought I did it back up pretty tight. But can't hurt to try.

So alongside cleaning the terminals I think I'll replace the pedal module with a second hand one off ebay (can't hurt to try at £15-25), clear the codes and see if any errors come back. Thanks all!

 

[LawrenceW]

LawrenceW wrote: ↑17 Jun 2024, 00:50
Can i jump in with a quick question on battery replacement - I plan to replace my battery on my Z4MC given the current one is 8 yrs old. Is it simply a case of old one out/new one in? or is there any coding requirements i.e. stereo? keys etc? Thanks
Yes it was just a plug and play for me, no coding required.

Brill, thank you!

 

[zomby]

Belated update on this: I replaced the accelerator pedal with part number 6789529, which was taken off a 2012 F20/F21 1 Series. It's actually a different shape to the original, but was compatible according to RealOEM so I thought I'd be better off going with a newer design. Long story short, after a good summer's driving the issue hasn't come back so it looks like problem solved!

Hope this might help others experiencing something similar.