I disconnected the Tach and EVERYTHING seems better. Rubber Banding CVT almost nonexistant.

However, I'm still puzzled by the water affect. I'll look at that ABS harness.

Thanks,
Peter

 

Okay, here's the next step of progress. I'm sure the battery positive short and perhaps even the water in the harness of the ABS were all contributing factors to the Tach's failure. Yes, all these discussions, as CAN wires being suspect are true. It could be the ABS harness short, as well as one of the modules on the network. If all the CAN wires look good, then disconnecting the correct, broken module would stop all errors except communication errors to the disconnected module....and that turned out to be the Tach.

 

*Disconnecting the tach resulting in no codes except for tach link errors, at first. Then, I got ABS errors 5D93 and I think it was 5D91....anyway, I kept resetting them while I was driving. Something like, no accurate wheel speed under 20kph. After about 5 stop and go's, the reset abs module didn't register those two faults, so I went fast and slammed on the brakes and activated the ABS, I did this several times and the faults haven't come back yet........this may be the end, but, I will still be testing.

 

A month later with the tach removed and the problem still hasn't recurred. My wife says it is time to buy a new tach.

Peter

 

Wow who would have guess the system is so sensitive crazy

 

Well good news is the tac is a slave it doesn't even require coding just pick up a used one

 

Just spent 8 hours checking can bus wire metered end to end and every connector no shorts no opens no grounds replace the TCM and errors are gone WTH it makes no sense

 

The problem is the Tach. It's the auxilary part of the instrument cluster and somehow develops some strange surges or shorts in it that send crazy impulses back through the CAN system and register false codes with other systems like ABS, and Instrument Cluster, Transmission Codes that made the CVT Transmission go into Limp-Home Mode and Wheel Sensors, etc. I found a wiring diagram somewhere and all of the circuits effected were downstream of the Tach's CAN lines. Took me a couple of months to figure it out. Got a new tach and all the faults that previously stored, never came back....
Before finding that the Tach was the main problem, the battery positive cable that went to the fuse box was worn through, under the battery and was touching the trans housing. Also found water in the ABS wiring harness the plugs into the ABS Module.....there have been known shorts in CAN wiring in that ABS harness area to also be from worn wiring that shorts...that wasn't the case with mine, however. Perhaps the surges from that battery positive cable shorting, somehow messed up the tach that made it send these crazy signals through the CAN wires. Six months and still no faults came back....that was definitely the problem with mine.

 

how is the car doing ? i have the same codes check all the wires for damage and water the bus read continuity any ideas ? were did you disconnect the tach i have and 2007 r52
Thanks Doug

 

Today i approached this mess different i connected a meter to one end of the bus at the DME and disconnected one device at a time watching the resistance to ground change hoping to find a short no luck , So i connected the DME and ABS only and started the car no intermittent issues started connecting each module one at a time and checking errors i took the advice of wilsemail1 and left the tach off the only fault is no message from KOM2 scanned running and not no additional faults ran a bunch of tests every thing worked , Drove the car for 45 minutes stopping to check faults no faults WTH a fault tach can leave you stranded oh well i will test more tomorrow a big thanks to pss-autosoft.net the software works great

 

Follow up i disconnected the tach drove the car a few day no issues no can buss codes , reconnected and in less then .5 miles the cars was crippled on the side of the road , i disconnected and drove it two weeks no issues what a dangerous piece of junk , replaced it with a junk yard tach and no issues since 2 months of driving , Next i will figure out how to connect a bypass switch , I have to wounder if this caused my transmission issues requiring me to replace it , I also wounder how many cars went to the crusher due to faulty tachs. ? also while trouble shooting i discovered see attached picture of the tran speed sensor note the outer jacket is very hard to roll back my question is were did the wire insulation go it was not on my bench this also was the case with the one from the junk yard the car was wrecked and the transmission was good

Mini CVT speed sensor

 

please describe rubber band effect ?
Thanks Doug in Raleigh