35d cranking but not starting

[TriX5]

Trying to interpret the symptoms you have and the fault codes you show. Judging by the number of different messages, it looks like the problem initiates from a bus error. Something is inhibiting bus comms between DSC, instrument panel, transmission, etc. I think those are on the K-CAN but I could be wrong. I am surmising that if major systems can't communicate, the DDE is programmed to shut down the motor to avoid bigger problems.

There could be a plethora of reasons for this and CAS module could be one of them. The bit that is troubling me, why is the AHM reporting 10.5 Volts? At such a low voltage I believe comms errors will start to appear.

[wogboy_9000]

Originally Posted by TriX5

Trying to interpret the symptoms you have and the fault codes you show. Judging by the number of different messages, it looks like the problem initiates from a bus error. Something is inhibiting bus comms between DSC, instrument panel, transmission, etc. I think those are on the K-CAN but I could be wrong. I am surmising that if major systems can't communicate, the DDE is programmed to shut down the motor to avoid bigger problems.

There could be a plethora of reasons for this and CAS module could be one of them. The bit that is troubling me, why is the AHM reporting 10.5 Volts? At such a low voltage I believe comms errors will start to appear.

From what was diagnosed, it seems the CAS was continually communicating with the DDE (when it shouldn't be). After a long drive, the DDE must be shutting itself down. I'll find out soon enough if it was the CAS module. I've been carrying my laptop and OBD2 cable with me in case it happens again.

Trailer module is on my list of things to investigate next. I haven't used to tow attachment yet as I'm waiting for a 13 pin to 7 pin round adapter to arrive to test the trailer lights.

[ard]

Not sure if youve seen this:



https://ia801005.us.archive.org/11/i...0Diagnosis.pdf


Interesting stuff on busses.


And this:


https://ia801005.us.archive.org/11/i...System%203.pdf


Do keep in mind that the admonishing about how you need to replace parts as pairs, order specially coded parts, applies to BMW dealers. Others have figured out how to hack all that.

[wogboy_9000]

Thanks for the info.

Quick update - same issue occurred again today. I had the laptop on me so I cleared the codes, but interestingly the DDE was completely unresponsive. I locked the car and left it for ten mins and came back and it was back online. I cleared the codes and away I went.

Tbh I was sceptical the CAS could cause this condition based on the feedback from others here and reading up on how the modules interact, but I was hoping on the off chance it would fix it.

So far, new battery and new CAS. Issue is still there. It appears to only surface on long drives however. Short drives don’t trigger the issue.

ISTA thinks the DDE is fine and once the errors are cleared, there are no errors or issues until the next time it stalls. Could the DDE be faulty?

I’m bringing it back to the dealer first thing in the morning. Needless to say, I’m not impressed.

[ard]

Read the documents I linked, then compare that to the depth of knowledge you are hearing from the dealer...... Id be shocked if they have even seen that.


I am thinking the CAS desnt 'talk on a line to the DDE'...it is a bus, no? So not a dedicated line, but a shared comm buss. Dunno, just wondering. Are they just spitballing or is someone hanging an oscilloscope on the lines and looking at what is actually happening? Again, someone that has internalized that advanced diagnostics manual would prolly do the trick.




GL

[halcyon22]

sir, please immediately pull out your dde and look at the plugs to see if they are wet. you have water or fuel intrusion in your dde and i expect a couple ounces of fluid to drain out of it

[TriX5]

Originally Posted by ard

Not sure if youve seen this:



https://ia801005.us.archive.org/11/i...0Diagnosis.pdf


Interesting stuff on busses.


And this:


https://ia801005.us.archive.org/11/i...System%203.pdf


Do keep in mind that the admonishing about how you need to replace parts as pairs, order specially coded parts, applies to BMW dealers. Others have figured out how to hack all that.

Fascinating read! Never seen a description of Bus systems like that before. Thx!

[wogboy_9000]

Quick update - issue is finally resolved.

I wasn't able to pick the car up myself, however the service manager said it was a faulty relay. Assuming it was the DDE relay.

Frustrating that the CAS module and battery were replaced for no reason, but glad to have the car back.

[ard]

Originally Posted by wogboy_9000

I wasn't able to pick the car up myself, however the service manager said it was a faulty relay. Assuming it was the DDE relay.

.

Wow.


That's it? All that drama and digging and you leave the issue unknown and frankly unresolved? (It beggars belief that a 'faulty relay' was missed in favor of CAS modules from germany....)

Hey, its your car and you certainly dont owe the xoutpost community a thing. (Well, maybe a bit but whatever)

But for someone that has a laptop, opens the hood, chases this stuff down- yet is fine with 'oh well, runs OK now' would just personally make me crazy. Especially after someone dumped $many-k into the car for no good reason.








But...we agree on the final point- glad its running.

[wogboy_9000]

Sorry, I forgot to update this.
Turns out it wasn’t a relay. After a 1.5 hour drive the exact same thing happened.
Connected ISTA+ and the DDE was offline again. The DDE didn’t come back online that evening either. Previously it was back up after 10-15 mins.

Had it towed back to the dealer and apparently it’s now starting and not throwing any codes again. Good times. Will update when I know more.

It can only be electrical. I wonder if the DDE is slowly failing and turning itself off after a period of time.