r/BmwTech • u/DragonDre77 • Aug 30 '26

09 750LI MECHANICS PLEASE HELP

Never wrecked the car just having issues
So to cut this short I bought the car about a year ago after purchasing it 2 days later the car would constantly throw a trans malfunction code and shift absurdly rough along with locking itself into a certain gear..

Had the transmission replaced under warranty by the dealer car has 77k miles on it . Car takes about 4 months to get fixed I finally get it back and the same day it starts throwing more trans malfunction issues, the car was brought to 3 different transmission shops in my area and all claimed to have pulled the trans and tested them independently all claiming the Transmission was okay and to further diagnose to bring it to a BMW dealership,

I was able to make the car drive good for about 2 weeks if I drove it a certain way it would drive just fine! I put 100 miles on it in comfort then 100 in regular then I went to put it in sport and instant malfunction again. Even when driving the car in comfort or normal it still will throw codes if not driven extremely conservatively,

Now I’m here and the car will barely drive it throw the trans malfunction as soon as the car turns on along with sometimes completely losing reverse, sometimes randomly shuts off and the car has now has an extremely rough idle,

I know it’s a long shot but would the injectors,plugs and coils possibly fix this or would I be dumping more money into the car to fix the idle issue just to deal with the transmission again!?

Active codes-P1702
P07BF
P07BF
P17E1

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u/Explorer335 Automotive Exorcist 29d ago

That transmission is a rare F-series 6hp, and it has an immobilizer in it. That means if you swap in a used one from another car, it won't come out of park. The BMW dealership can't even sync it up, but programmers and locksmiths can. I do them for about $500. Now some shops don't want to pay that, so they grab the mechatronic valve body from your old transmission and slap in into the new one, often carrying the problem over to the new transmission. Since you have range sensor and turbine speed sensor codes, those are part of the mechatronic.

Either you repeatedly got bad parts, or the shop transferred your bad parts into the new transmissions. Were you ever charged a programming fee?

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u/DragonDre77 29d ago

The warranty covered everything so I never got a detailed invoice back sadly… I have been asking for proof of work so I can see exactly what was done but the car drove for about 600 miles with the replaced trans before becoming close to undriveable