Unable to communicate with engine or transmission over OBD?
 

I drove 10 hour roundtrip through Washington in the pissing down rain, passengers window switch got wet and fried... then the transmission went 'clunk' and went into fail-safe mode.

After getting back home, next day I put it in reverse, and clunk - engine even turned off! I knew my battery was getting weak, so I replaced it, and reverse worked again for a day, although still in fail-safe mode. I also replaced the passenger window switch, and it too is working ok now.

I took it in to an independant shop, they said the OBD is NOT communicating with the engine or transmission, so they can't diagnose at the moment.

Any ideas what module/sensor/fuse would be at fault? The OBD can communicate with all the other modules just fine.

What year x5?

what year x5?
 

2002

Depends on the production date. But make sure the 20 Pin cap is on under the hood. If not find someone with OE BMW tooling to scan the car. Good luck

20 pin cap
 

I'm a noob when it comes to this stuff - can you let me know what this 20pin cap is, and where I would find it? I know they were trying to access the systems via the OBD which is lower left of the dash, but didn't know there were other areas to tap in?

Is it worth removing/cleaning the contacts on the ECM (where is it?) or flushing the transmission - if that's possible? I would very much like to get the codes off this thing so I can figure out what the heck is going on.

John

the 20 pin under the hood was on early production cars
legislation demanded obd sockets within 1 metre of driver
the obd in the dash is the only access on your car .

there is a large black box of electronics in the bulkhead under the hood . probably on the right / passenger side on your car I think has 4 hex bolts on lid .
these can suffer water ingress causing havock with electrics .

I've had this happen twice to me where I had the exact same symptoms...pouring down rain, TFS on the dash and couldn't read codes. I've yet to figure out what it is, replaced battery just like you and eventually things fixed themselves. I've spoken w/ my transmission rebuilder and we discussed things like checking harnesses connected to the transmission and/or wheel speed sensors. I personally don't have the same readers that dealerships use, so this may be what is needed since my Peake readers didn't tell me anything specific in regards to transmission or speed sensors when it finally started connected.

It was bad enough once that each time I'd put the car in gear, it'd die as well, sounding like something was jammed inside the transmission. After about 5-10 attempts (it was a couple of years ago), I rolled the X5 in neutral w/ the engine running and bumped in into gear and finally got it start acting normal again. Recently I got the TFS about 3 weeks ago while on a trip to Reno. I still wish I knew exactly what it is, but it stopped after a couple days of sitting in the garage w/ a propane heater keeping it a nice and toasty 70*. I hope we get it figured out before it happens again.

Problem found - was the TCM
 

Yup, as suggested - water ingress into the compartment that houses the ECM/TCM, etc. There is corrosion on the pins, which is a PITA to remove - but already after an hour cleaning it - I reconnected everything, and it's working 'much' better. Reverse is still intermittent, so I'm going over it again. Could the tranny 'reset' (pos 2, hold accel 30 sec, then brake 10 sec, then start) help with that, or is likely still the corrosion?

best to leave the car indoors with the lid off the box for as long as is practical to allow any moisture to evaporate .
don`t be tempted to use excessive heat to assist drying .
the pins will require thorough cleaning and their sockets cleaned . also if you can close the sockets a bit more to have a tight grip on the pins .

Suggestions for cleaning
 

I've spent quite a lot of time cleaning it up, and it worked for about 15 minutes, but then went back to TFS mode. Any suggestions for how to clean the connectors, I very thin pipecleaner but more abrasive would be great, but haven't seen anything on the market, but perhaps I don't know where to look.

Also - one of the pins is quite wobbly, I'm concerned that it's a bad connection no matter what I do - any ideas on how to fix a bad pin? If someone has a pin-out diagram, at least I could determine what the bad one does, it could just be a ground and not be 'essential' to the operation.