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peterpete190, Auto Technician
Category: BMW
Satisfied Customers: 29116
Experience:  Over 17 years diagnosing and repairing vehicles.
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Second opinion] - I got the code 4f85 the transmission was

Customer Question

Second opinion] - I got the code 4f85 the transmission was rebuild and the problem was not solve
JA: Just to clarify, what's the exact code? And have you tried to reset it?
Customer: Code 4F85 the sintoms are when the car is under aceleration and shift from 4th to 5th gear the gear slips and the engine revs up and goes to fail mode also when driving slowly sudenly the transmission goes to fail mode
JA: What is the model/year of your BMW?
Customer: 2005 525
JA: Are you fixing your 525 yourself? What have you tried so far?
Customer: no at the transmission shop
JA: Anything else you want the mechanic to know before I connect you?
Customer: the transmission was rebuild using a good quality repair kit and the problem remains the same what do you think that it may be the problem We tested the TCM and is OK
Submitted: 11 months ago.
Category: BMW
Expert:  peterpete190 replied 11 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

If you have not had the wiring checked leading from the TCM to the transmission this needs done.If any issues are found with the wiring this will need resolved to correct this fault.If this is or was checked already and found o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 11 months ago.
First I would like to know what is the description of error code 4F85 according to BMW manual
Expert:  peterpete190 replied 11 months ago.

4F85 code is a faulty transmission control module (located inside the transmission) according to BMW documentation. There were some issues where this code was a result of a bushing failure on the input shaft in the transmission but unfortunately I dont have the document info on this here. The entire shaft needs usually needed to be replaced which is arond $500 to have done.

Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.A 5 star rating is appreciated.Thanks Pete

Customer: replied 11 months ago.
This contriol module is the TCM or the valve body?
I am aware of the bushing of the shaft failure, how can identify is where the problem is, do you know the tolerance for the dimension of the bushing in order to check it?
Expert:  peterpete190 replied 11 months ago.

It is the TCM inside the transmission which I believe is located on the valve body.

I dont have the tolerances or inspection procedure on this shaft myself or bushing unfortunately.You may have to have this inspected by a shop to see if the shaft needs replaced.

Customer: replied 11 months ago.
according to my mechanic tester error 4F85 is not an electronic problem i have the TCM checked and it is fine.
Do you think that the bushing problem may cause the faulty shifting from 4th to 5th gear? the transmission slips and engine revs up then gets in emergency mode
Expert:  peterpete190 replied 11 months ago.

Yes for sure,this will cause excessive play which in turn can cause the transmission to operate incorrectly and cause this issue here.If the TCM is fine and wiring to the transmission is fine as well then this usually indicates an internal mechanical fault needing repaired and the bushing/shaft is most common with this code set here.

Thanks Pete