thomassteen

Thinking some more about this, it sounds like something happens when the systems in the vehicle initializes. Once initialized successfully the car works as expected - right?

From what you have tried it seems like heat improves the situation. You also mention that changing the connectors in the ECU seemed to help for some time - AND that there was sign of corrosion on the connectors.
To me this points towards water somewhere in the electrical system related to the ECU. Maybe the wiring loom or some of the sensors related to the ECU.

You said that you have tried reading out error codes and clearing them. Have you tried clearing them, and then reading out the codes after the problem has occured (such that you capture the codes related to this problem only)?

zimguy

Hi Thomassteen

I have pretty much identified the following as an indicator if the car will start......it is regarding the lines that come up behind the rev counter (temperature/over-rev) ...basically if the lines come up fully (when cold they go to about 4000rpm mark) then the car will fire up, if the lines just come up a little (just at the 5000rpm mark) then the car will not start at all.

There is a video on youtube done by someone else which shows the exact same problem I am having, but the repairs they talk about in the video do not make any sense to my specialist. On this guys video you can see the lines I am talking about.The guy in this video doesnt turn the key on and off like I have to, but you get the idea.

Today my haptic feedback gave up on the iDrive and the iDrive system was frozen on the home screen.

(youtube video if you are interested )

zimguy

Just seen your second posting Thomasteen. You are correct, it seems that if the car initialises correctly before cranking/turning.....then it will fire up and run fine. (As I said above there may be a couple of faults that linger on the iDrive and other times it is completely clear once the engine is running)

The garage has done exactly as you suggested with the codes, it seems to be the same faults that come back once the car is cleared...then the issue happens again the next time you put the key in...the same codes/faults are there.

H F

Is it possible that it could be the fuel controll module..

thomassteen

Can you list the faults they read out?

It sounds like you have a faulty engine coolant temperature sensor - or some bad connection to the sensor. If the lines behind the rev counter only comes up to 5k, then the DME "thinks" that your engine is warm and at normal operating temperature, and will set all parameters accordingly. This would also explain why there does not seem to be a problem when the engine is warm - then it most likely get the temp reading correct.

thomassteen

Here are some values from WDS you can ask your workshop to check on the sensor - in particular if the readings are stable:

Coolant temperature sensor
The coolant-temperature sensor is destroyed in the case of short circuit to positive.
Target values for resistance check:
Resistance at 20 °C: 2.5 - 3.0 kOhm
Resistance at 50 °C: 0.7 - 0.9 kOhm
Resistance at 100 °C: 0.12 - 0.17 kOhm

A note: As you can see, lower resistance values correspond to higher temperature readings. This would confirm the theory of a bad connection to the sensor. Ie. the resistance is higher than normal leading the DDE to believe the engine is warmer than what it really is.

They should measure the resistance in the connectors at the DDE unit to make sure the full cabling between sensor and DDE is checked. See attached image for details.

zimguy

Hi Thomassteen,

Thanks for all of this comprehensive info and advice. I have taken this to my garage and asked them to investigate. He is more than happy to follow your line of thinking.

As a side note: On that youtube video I posted you can see that the guy replaced the ECU relay, my garage has agreed to also do this.

There was someone else on the South African BMW forum with the same problem who had it diagnosed to be a blocked fuel filter which was causing the fuel pump to over-heat which was close to some electronics which then got too hot. He has told me that the problem was solved after replacing the fuel filter and a couple of small nearby components.

This all seems really strange to me, its almost as if there is a communication corruption on this CAN which could be caused by of the components...but always shows the same set of crazy errors. This would explain why people with the same symptoms have fixed it through different ways.

I have also come across a number of people who have this issue and could not fix it. Car scrapped

I will report back to you here after the garage has done the work

Thanks agian

thomassteen

Please also get them to send you the list of the error codes that they read out.

zimguy

Hello again...

So I am a bit nervous to say anything in case I jinx the car, but.............

Following the guy on the youtube video above, my garage changed the blue ECU relay and the car appears to be working. To be honest, we dont understand why as the ECU relay he removed seemed perfectly fine, but you never know.

We are more convinced that its a dodgy wire in the loom near the ECU so each time we work in that area the loom is moved around and it makes a good connection for a while.

I am due to trade the car in on Saturday now, the dealership was kind enough to extend their offer and wait for me to fix this.

Thanks for the input on this problem, I really do appreciate the support and ideas.

So...change the blue ECU relay....oh well!