The error code wheel of fortune continues - This time P1242

[JoergM]

Originally Posted by drover

WG's never came with a dip stick..

Oil type may cause problems but just starting up overfull won't other than blowing out breather, too low will foam up and miss or stick changes....
Have a look at the right front of your gear box, there is a large electrical connector, unplug and have a look inside , if there's oil there, thats your problem, new plug is cheap and easy to replace but care is needed as it screws into a very expensive circuit board inside the gearbox... replace plug is available form Benz, cheaper and easier than any dealer.... I always used Penrite in my W5A580 tranny.... as well as in my 8HP70 now.

Otherwise disconnect battery and unplug the TCM and other magic boxes sometimes it works whether fully clearing memory or by ensuring better contacts I don't know.

Thanks a lot for the additional hints. I have this electrical connector already. I bought one from Mercedes Benz, offered on eBay by someone in Europe. It was next on my list to replace. I added the tranny fluid you had listed on your all WG CRD thread, so I should be good.

I disconnect the battery every night at the moment, to save some power, since the car does not move a lot. I removed the center console today and will unplug and clean the TCM tomorrow as well as the connector and see how this goes.

[drover]

When I replaced the connector on mine, be many years ago now it was $29 I think from a Benz dealer, I actually used a tranny shop as while a simple job when I checked out the price of the circuit board it screwed into I thought the tranny could do with a good flush as well, well thats was my excuse anyway and it sounded better than, "Oh Shit ! " if I broke it.....

TCM, shift selector or plug socket are the likely contenders, I think ??? so long as correct oil in box, of course box may need a proper flush if it only ever had a dealer service then the tranny would have a lot of sludge in it after all these years with sticky solenoids....... I will have a look in my shed and see if I still have the dip stick I made up, I may be able to measure how far from where it seats on top of the tube to where I marked the oil level, you never know your luck ............. I only ever just dropped the oil, that was in the pan, new filter and then topped up the box, if Jeep reckoned it was good for 100K km then my half change every 35K km was better even if I only got put 75%...

[JeanLuke]

The plug on the transmission won't directly cause a missing TCM error. It causes other errors. I cannot recall which, but would expect them to relate to solenoids and/or sensors.

What the plug on the transmission is known to do is leak oil which can wick up the cable and take out the TCM (which I guess will become missing TCM errors). You can tell immediately if this has happened by the smell of transmission oil at the TCM. It happens, but is not particularly common.

The CAN bus transport layer operates at a very low voltage (3.5V from memory) and therefore is very susceptible to dirty connections. It does not have the "grunt" to break through even a little extra resistance. This is by far the most likely culprit.

[RTB]

Originally Posted by JeanLuke

The CAN bus transport layer operates at a very low voltage (3.5V from memory) and therefore is very susceptible to dirty connections. It does not have the "grunt" to break through even a little extra resistance. This is by far the most likely culprit.

Not that it matters, but I think I read zero to 7.5V in the manual. I am thinking of connecting up the oscilloscope to mine to see if I have clean rising and falling edges on the signal, or if there is any interference breaking through at all.

Dirty connections, dirty earths, however slight are problematic to bus communications.

[drover]

Found my WG dip stick but sadly the marks cant be made out good enough after all these years...................
The leaking socket will cause shift problems and other dramas not always throwing codes I found out, when I discovered mine had a leak I had shift problems and a code for a module or solenoid, it was the oil shorting things out and it was only a small weep around the lock ring but inside was a lake.

[JoergM]

Originally Posted by Farwest

Wouldnt ever rule out any problem solving solutions that owners have experienced...personally...I ALWAYS start with the 'no cost' attempts...then work my way up the 'cost list' hoping to have solved the issue prior to reaching the most expensive... and generally the approach used by 'half hearted workshops'...possible solution...if you have ANY mechanical skills...and you dont really need much with what is available and viewable on U Tube...then work your way through it...better you 'tinker' with your own machine...possibly finding other 'little issues'...then pay a workshop for exactly the same effort and probably NOT be made aware of 'other issues' or failures in the making....only my opinion...fully aware its worth nothing

That's exactly my thinking too. I restored an old W123 Mercedes Diesel this way. Only involved the workshop for telling me what I need for a roadworthy and then worked my way thru. And as you said, once you start working you will find plenty of other things (which I did and fixed them right away before they will bite me in the ass down the road and then have to redo the whole thing again). Since some spare parts are almost impossible to get, or cost a shitload of money I tried to fix it first with very little money involved (only paint or rust remover, or a couple of screws or rivets etc.) and only if there was no other choice I tried to source it used and if not available and only then I bought new parts unless it was something I could get off Rockauto for rather small money right away. I rather took the money I would have spend for a mechanic and invested it in tools instead. Took me 1 1/2 years but ultimately this car runs like a dream and has barely any rust left. In my 4 1/2 years I am here now and actually own cars (haven't own any car prior since I did not need it or had mostly company cars) I have never been at a mechanic to get something fixed. My wife does not really like it since the thinks going cheap cause lots of other troubles and I would waste all my time, but that's the only way how you learn things and once you acquire that skill it will be with you for the rest of your life and I can even teach it to others.

[JeanLuke]

Originally Posted by RTB

Not that it matters, but I think I read zero to 7.5V in the manual. I am thinking of connecting up the oscilloscope to mine to see if I have clean rising and falling edges on the signal, or if there is any interference breaking through at all.



Dirty connections, dirty earths, however slight are problematic to bus communications.

The PCI bus runs at 0V=low and 7.5V=high. The CAN bus runs at 1.5V=low and 3.5V=high. The WG has both present, with the comms between the ECU, ABS and TCM are on the CAN bus.

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