C5 X7 gear selector stuck and will not start (HELP!?)

[Kupsberg]

Hi all!

C5 2008 2.0HDi, 136hp SW Exc. Automatic (AM6)

I got my old queen from under a sheet of snow a week ago after three months of standstill. Everything was working fine other than the windscreen clearing button did nothing (happens occasionally. As said before, this vehicles blowers in and out has never been working as one would think..), went to carry out the yearly MOT, which it failed due to a sub frame bushing gone bad. Drove home 80km and shutted the engine behind the garage. Ordered the needed parts. Next morning tried to start the car and drive it to the garage but the battery was dead (-10°C). This vehicle has a speciality to deplete its battery in few winter days if not disconnected. But for overnight! This was new. I put the battery on a charger and waited a day. Better result, instrument cluster would wake up normally, but engine would not start. It was also complaining about electronic secondary brake but it's fine, it worked at it should. Noticed that the gear selector shows just a dash and the gear lever is stuck on P, like really rock solid!

Had to leave it for the week and now got back to it and trying to resolve the issue.

Tried reading this forum a bit to have a clue what could be wrong. Today I tried changing the black relay on the drivers side footwell (LHD), there were two white, one yellow and one blue wire coming to it, 5 pin narrow relay. Changed it to a similar type 25A/15A relay but had no effect. Checked the F7 (transmission interlocking) fuse, it was also fine, also the G36 15A fuse on Fusebox B. I had bought a second hand BSM anyways to change it to the vehicle as I think it is causing the still remaining AirCon issue ( ) that has persisted for a veeery long time. Last summer I went through all the loomings etc and came to a conclusion that a relay had gone bad on PSF1. Anyways thats another topic, but this lead me to an idea of changing the whole BSM to a new new, which I now did but did nothing to the matter at hand. Also changed the battery to a different fully charged one, no difference to the matter.

Checked also the situation on Diagbox and it showed some CAN issues on BSI (no connection to automatic gearbox module) and also diagbox was unable to read anything from automatic gearbox module in fault finding, so I guess it really is unreachable.

Does anyone have any fresh ideas? I'm a bit frightened that all is pointing towards the AM6 gearbox's control unit. Low voltage has the tendency to hurt control units..

All help is welcome! Thanks in advance!

-J

[Kupsberg]

Diagnostics continues to no avail.

I noticed that if you wake the car up by having the doors open when connecting + terminal and inserting and turning the key as a first action the P indicator is shown on the dashboard/IC. The P stays visual for 5 seconds after which it changes into a dash-line or the whole IC turns into full power saving mode. Engine won't start at any moment. I've had the car on jump wires for half an hour now and it still goes immediately (after ~ 5 seconds) to "economy mode". After disconnecting the jump wires the battery voltage shows 12.46V, even while webasto is running.

There was a bad looking wire joints on the right hand side of the drivers footwell (LHD) which I re-did (soldering + socking). I have tried changing to new and old the black "interlocking" relay, but does not effect anything. Also the counterpins look okay on the relays base.


I'm a bit lost on ideas where to look next..

-J

[Kupsberg]

Back to report!

Finally gave up on looking for miracles in the fuses & relays area.

I dug up the transmissions control module. This required removing the intake air manifold and intercoolers upper hose. Marked the positions with a marker but I quess this was for nothing as there was a mark on the actual module.

Just opened it up and got my answer. This surely is burned and no wonder it does not show up in Diagbox. I'll throw this one in to the trash can and order a new one..

I hope this monologue will help someone else in the future.





-J

[wurlycorner]

Good work finding that and thanks for updating the post with the details.
Let us know if swapping the ECU fixes it all ok?
Any thoughts what has caused that to burn out? What does that component drive? Is it maybe a solenoid that's gone short circuit?

[Kupsberg]

Got my new ECU today for the gearbox, and now I'm wondering if it requires any pairing on Diagbox to get it functioning correctly..? Wouldn't want to be changing the whole AM6 gearbox next! Anyways, I'll install it tonight and we'll see what it says.

"Any thoughts what has caused that to burn out?"

-I'd say it was the undervoltage in -15°C that eventually got to it. Undervoltage tends to have a way to burn circuit boards. But what causes my battery to drain so quick? That would be nice to find out!

-J

[GiveMeABreak]

You must ensure that you undertake the following if you have replaced the ECU with another one:

• Writing the value of the oil usage counter in the new automatic gearbox ECU
• Perform auto-adaptive initialisation
• Carry out a learning procedure of solenoids and oil pressure regulators
• Carry out a learning procedure of position N of position sensor of gear selector lever

[Kupsberg]

New gearbox ECU installed and car is up and running brilliantly! Gearbox seemed to work normally after the ECU change but I did not drive it that far, only drove it inside the garage to do the original task of changing some bushing on the subframe..

You must ensure that you undertake the following if you have replaced the ECU with another one:

• Writing the value of the oil usage counter in the new automatic gearbox ECU
• Perform auto-adaptive initialisation
• Carry out a learning procedure of solenoids and oil pressure regulators
• Carry out a learning procedure of position N of position sensor of gear selector lever

Hi Marc, and thanks for the info!

Writing the value of the oil usage counter in the new automatic gearbox ECU

I'm wondering how to perform this? The rest I think I can figure out in Diagbox. But how would I know the oil user counter as the old one got black out? Is it still visible somewhere else in Diagbox?

Seriously would like to change the gearbox oil as well but bit hesitant as she has done already 421k km and the last gearbox oil change I could see has been carried out around 160k km..? The gearbox does work fine but regarding towing caravan or trailer with two sleds on it probably wouldn't hurt to change the gearbox oil as well?

-J

[GiveMeABreak]

If you don't know the previous value stored in the ECU before it was removed, I suggest you change the oil in any case and then just reset it. Probably best to change the oil before undertaking all the other procedures to be honest.

[Kupsberg]

Yes, I came to the same conclusion and this what I will do! Now wondering if its okay to use the jws3309 for the gearbox as its one of the earliest generation X7 2.0hdi (136bhp 2008)? When does the Euro4-Euro5 change occur on the gearboxes?
I had to drive the car for 200km and the gearbox seems to work fine without any actions taken. Just to point this out if it might help someone else in future. Although I would not advice this as you can never know about how good the match is.

-J

[Kupsberg]

I changed to Mobil 3309 ATF, and I will now drive a ~200km trip this week and change them once again. So after this it should be good enough considering her mileage overall. After the first change the gearbox started behaving really smooth!

Notes for other crew (and to my future-self..)!
1. When changing the ATF, remember to have engine idling whilst the last phase of the fill up. Without this you wont be able to fill the required 3l, rather just 2l.
2. After resetting the TCM the behaviour of the driveline significantly changed! Feels like there is +40bhp more on the vehicle. After this knowledge I highly recommend to change the ATF >2 times at least if there has been a longer gap between last change of ATF. The compensation of "oil ageing factor" seems a lot stronger that I had anticipated myself.

-J