Well, it's been an interesting last few days with my 2003 R50 CVT. On Monday, my wife was driving it in traffic and it started bucking a lot while coming to a stop - she put it in SD mode which stopped the bucking. However, once traffic started moving again, the dreaded no "upshift" was happening. The car could get to about 40-50mph at 5k-6k rpm. Needless to say, it was a slow and gas-guzzling commute home for her.

Last night, I finally got BMW INPA and DIS working on my laptop and communicating with the car's ECU. I reset the clutch and ratio adaptations and everything seemed to be back to normal - shifting was back to usual...until I tested it on the highway. Slowly the RPMs kept creeping up and up, until after exiting the highway I had to creep the last 2 miles home at 30mph and 5k-6k rpm.

But, during those last 2 miles, finally the ECU decided something really was wrong and "EP" and "SES" showed up, which I was very thankful for - I could now pinpoint the problem! Checked the code and it was "1786 DME: Gearbox-ratio actuator - measuring-range or power-output problem"

This is the stepper solenoid on the valve body that controls the position of the main drive pulley. It makes sense that it would fail - it has been constantly controlling the drive pulley for the last 121k miles. The erratic behavior is likely because it intermittently starts to function, but then fails.

The part itself is about $370:
http://new.minimania.com/web/Item/NMD5071/InvDetail.cfm

Replacement doesn't seem like it would be terribly bad - pulling the transmission pan, removing the valve body and replacing the solenoid. The transmission doesn't need to be removed from the car or disassembled. The Minimania link describes one possible difficultly with fitment though - the older valve bodies have a protusion that serves no purpose that will need to be removed. They say it will fit though.

I'm hesitant to throw money at the CVT for this repair, as I eventually plan on replacing it with a 6-speed manual, but this could be a much more economical repair in the meantime. But, then again who knows when another CVT component might fail...

If I end up getting the solenoid and putting it in, I'll update this thread with the results.

 

Well, an odd update here. The MINI sat unused for about 2-3 weeks. Figured I'd clear the code and drive it a little one night just to keep the fluids moving, and go figure, it drove completely normally.

The next night, took it for a longer drive, including highway driving, trying all shift modes (D, SD, Manual), and also did a few runs in kickdown mode. Everything was normal - no sign of a problem.

Of course I don't really think it's fixed itself - the stepper motor must be intermittently failing, and it just so happens to be working again after having a rest.

For now, since it's driving normally, I'm not going to go forth with the stepper motor replacement until the problem reappears. Will update with further developments as they happen...

 

As expected, got stuck in low ratio again last Friday while slowing down from highway speed. Thankfully was close to home and limped it back. "EP" and SES came on almost immediately - same code, 1786 DME - the stepper motor on the valve body.

I will probably be taking the hit and having Way put a 6-speed manual in. Even though it's far more expensive, since I plan on keeping this car indefinitely it's probably better than putting money into a transmission that is certainly on its way out. I'm pretty sure in addition to the failed stepper motor, the main bearing on the transmission is shot and who knows how much longer the metal belt will last among other internal CVT components...

 

Did you managed to find a fault ? I have same symptoms. Changed oil and filtel (old oil clean, no metal shaves). Had stepper motor fault (stepper motor been replced to a new), TCM module replaced. Gearbox has no noises.
still no luck :( help

sometimes drives fine. Spoke with one guy who is repairing automatic gearboxes for 30 years. But even him can’t tell where is a problem. He said mainly pulleys goes but that causes gearbox completely not to work. He said try to check electronics

 

Was the center displaying "EP" and were you getting the 1786 DME code?

I think multiple things can cause the CVT to get stuck in the low ratio. It's also certainly possible that some other sensor is causing the stepper motor to behave incorrectly, but it's the stepper motor code that gets displayed if you are getting 1786 DME.

Did you do all of the adaptation re-learn procedures, etc.?

With no one having solved the problem before me back when I had it, I didn't want to take a chance and waste the money on the stepper motor, only to have it not work or have another internal part fail. Since I'm planning on keeping the car forever, I swapped for a 6-speed manual, and 45k trouble-free miles later, I have no regrets on that decision.

 

Rational speed sensor Located on the transmission. I spent many hours and transmission flushes to finally come to my senses and replace the speed sensor on or CVT equipped Mini. Before replacement I had codes for stepper motor,TCU, Instrument cluster etc. Basically pointing me in 100 different directions. In thinking about it it made sense to me as the speed sensor is nothing but a magnetic pulse generator same as a crank sensor, and I've replaced a lot of crank sensors over the years. So I'm Happy to repot the Mini is doing well 8 months later. I hope this helps.

 

adaptations been done few times but that doesn’t make difference. PCM been updated to latest software.
Next step to check wiring and sensors.
Is there any chance to see on DIS or other software how every sensor working? Maybe speed sensors sometimes sends wrong signal and that causing problems. I had before peugeot and crankshaft sensor sometimes was playing and that was causing engine to stop. Most times was driving fine and was no faults on PCM. Maybe here similar problem with a sensors.
I managed to get p1786 (stepper motor) fault two or three times but only while I was driving over limiter for maybe 30s. Other times fault won’t come up.
Also noticed if you driving while cvt stuck in 1-2 gears for about 10miles in city it starts shifting again.
Its very erratic problem.

 

thanks for your reply. Yesterday I started thinking about this sensor. I’ve just ordered one from aliexpress for 40£. I’ll let you know if this solved problems.

 

Hopefully that sensor fixes it for you.

After mine got stuck in low ratio, it would never go back to normal, so your symptoms are a little different than what I was experiencing.

When mine would get stuck, it was always a 1786 code and it was triggered quickly too, so it was different from Black Forest's problems too.

 

Glad to hear you have one coming. It was one hell of a battle on my end narrowing it down. Please let me know how you make out.

 

Hello Any updates?

 

does this issue got resolve? I am having the same issue on my cvt. Thanks

 

I ended up going to a 6-speed manual, so I'm not able to give any solid advice on fixing the CVT. I haven't followed the issue too much in the past years, but I think some have been able to fix it with a sensor, and others have replaced some internal components with some limited success.

If you plan on keeping the car for the long-term, strongly consider putting a 6-speed manual in. I'm coming up on 8 years and 70k trouble-free miles with it....

 

https://www.aliexpress.us/item/32568...2usa4itemAdapt

was this the speed sensor? If not which one? If yes, did it fix it?

 

You can get the genuine MINI part again, but its pretty high priced. For a short period its was on back order.

https://www.ecstuning.com/Search/Sit...h/24357518732/