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.

I've never heard the part of holding the brake pedal for 10 seconds, but I don't think it can hurt either. I've yet the check the ECM/TCM area, but mine stopped giving me this issue the following day, so who knows for sure. I'm still curious to see actual pics as to where the water is getting in at so I can remedy it when I get back home.

Something else I discovered that's a "big deal" - I cracked open the case on the TCM, and there was a LOT of corrosion on the circuit board, between the pins on the various chips - this is as important to remove or more than what builds up on the pins and connectors. I'm about to pull the ECM and do the same to it, I bet it will be bad too.

Sounds like a can or two of Radio Shack electronics parts cleaner and some dielectic grease might be in order.

Took the TCM apart, there was a lot of corrosion on the inside too, all that has now been cleaned up - but still the FSP message continues. I've even taken the ECM apart, it was clean however. I'm a bit stumped, wish I had a TCM to try rather than buying one outright, as there may be another problem.

I cracked open the TCM, and cleaned it out inside - it also had corrosion there. Reverse now works, and when I first start out, the tranny goes back to normal - but soon enough TFP returns... so now I'm a bit stumped. It does start to stutter around 60 km/h, and after 5 sec or so of that, once I slow down - then TFP turns on and I'm back to 3rd gear only. I need to get the OBD read again, me thinks - I hope there's something to go by... any thoughts, anyone??

I cracked open the TCM, and cleaned it out inside - it also had corrosion there. Reverse now works, and when I first start out, the tranny goes back to normal - but soon enough TFP returns... so now I'm a bit stumped. It does start to stutter around 60 km/h, and after 5 sec or so of that, once I slow down - then TFP turns on and I'm back to 3rd gear only. I need to get the OBD read again, me thinks - I hope there's something to go by... any thoughts, anyone??

PROBLEM RESOLVED!
 

I believe that many owners are getting shafted out there on rebuilt transmissions when it's simply not necessary:

First off - GET A OBD reader! It is essential if you want to figure this stuff out on your own. Deal extreme have Carsoft 6.5 and all the cables included for $60 - you can't go wrong.

Symptoms:
Transmission in fail safe mode
Reverse gear stopped working - when put in reverse, it would either do nothing, or actually shut off the engine!
hestitation around 60km/h, transmission felt very rough

Steps taken:
Battery was weak - replaced it with a Motomaster eliminator $160
Removed and cleaned the TCM and connectors - actually open the TCM, and use electonics cleaner to remove any corrosion. Check the ECM while there.

Was still intermittent going into TFP mode, and the check engine light on - used my OBD, and read P0721 code on the transmission. This is a pulse generator, crank shaft that take 10min to remove/install, it's $130 aftermarket part.

Cleared the 'check engine' code with ODB, and HOLY CRAP - my tranmission is working 100% normally again.

BMW wanted $3000 for a new TCM and 7 hours labour to replace all the connectors. That did not include the pulse generator or labour for that either, in fact they never even mentioned it as being a possibility.

All told, I saved about $2500 - $3000 on doing this work myself. PITA, yes - but well worth it.

If a moderator reads this, perhaps an entry in the 'how to' section under tranmsissions might be appropriate?

Post like these where BMW diagnostics vs trial and error lead to the real issue. I had a similar situation w/ my 7 where it wouldn't run, had it towed to a shop who wanted to do about $3500 worth of head removal, carbon cleaning, fuel system replacement to discover on my own time (in their parking lot) that it was a clogged cat once I removed the pre-cat 02 sensor. Drove the car (a 1" hole does make a lot of noise btw) to the exhaust shop, and $200 later I was running perfectly and back on the road again...and just like your situation, NOTHING they suggested I do would have even gotten them in the ballpark of what wsa wrong. Threads like these make these kinds of forums invaluable.

Glad you sorted it out and thanks for sharing.
Going back to the main title of your thread "unable to communicate with .....over Obd",I think a big thanks to M5James is also in order,since he suggested you to use electrical contact cleaner spray on your corroded ECU connectors/pins,which in these cases is imperative..:)

OK, what is TCM? any picture?