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Ask Mike Kelly Your Own Question
Mike Kelly
Mike Kelly, Auto Service Technician
Category: Car
Satisfied Customers: 5470
Experience:  17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.
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bmw e46 auto transmission trans warning light comes on when

Customer Question

bmw e46 auto transmission
trans warning light comes on when car reaches 10mph does not seem to go into limp mode but it does change down to 2nd to 1st harshly every thing else seems fine .sec mode works ok.
if you leave car parked for approx half hour warning light goes out ,then same thing will happen as above .
fluid filter and ecu changed made no difference .
Submitted: 4 years ago.
Category: Car
Expert:  Mike Kelly replied 4 years ago.


Hello, welcome to Just Answer/Pearl. My name is Mike, I will
do my very best to assist you with your question today.

Is the system setting any trouble codes?

IF so do you know what they are?

Also when the fluid was changed,how was the condition of the fluid?

Customer: replied 4 years ago.

only codes that have come up are as follows


variable valve gear ref sensor P2852


variable valve guide sensor P2850


alternator communication P28d7


nothing on gearbox


fluid wasnt that bad , only got about 5 litres out of box no bits on sump magnet


 

Expert:  Mike Kelly replied 4 years ago.
Ok the alternator code can and will cause this issue,low voltage to the alternator can throw the electronics of the system out of sync and result in your issue.What I would suggest as a first step is to have the alternator load tested to determine the voltage is not dropping.
Customer: replied 4 years ago.

hi will try get it checked tomorrow and let you know the outcome

Expert:  Mike Kelly replied 4 years ago.


Thank you and don't forget to rate the
answer for me, you can always respond back to this question at any time even
after rating.

Customer: replied 4 years ago.

HI SORRY ITS BEEN A WHILE HAVENT BEEN ABLE TO WORK ON CAR AS I DAMAGED MY THUMB


ALTERNATOR WAS NOT UP TO THE JOB SO ITS BEEN CHANGED BUT SAME FAULT TRANSMISSION LAMP WARNING LIGHT IS ON STILL CHANGES DOWN FROM 2ND TO 1ST HARSHLY .HAVE NT GOT THE SAME CODE READER AS I USED LAST TIME ,THIS ONE IS SHOWING NO CODES.

Expert:  Mike Kelly replied 4 years ago.
The valve body in the transmission seems to be the culprit in this issue,what I would suggest is to have the vehicle hooked to a transmission scan tool and test driven. What this will do is monitor the shift times and the pressure readings from the transmission and the valve body. From the sounds of this there is a pressure issue coming from the valve body.