Lets break this down:
Quote:
Originally Posted by l_turn9
Hello, Bought this car last year without enough due diligence and now I'm paying the price. The AT shifted buttery smooth until it stopped up-shifting out of 1st.
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Given the car was working at time of purchase and did so for a decent amount of time, I doubt any pre purchase inspection would have uncovered anything. It is a 13 year old car after all. Also, actual limp mode on a 722.6 is 2nd gear however you could actually be starting out in 1st. .
Quote:
Originally Posted by l_turn9
The indicator lights that show when it is in Sport or Normal mode are blank when the shifting stops working.
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The shifter on these cars is an electronic device that communicates with the transmission controller, you _NEED_ a scan tool to look at live data and codes. The shifter might be commanding the trans to shift in manual mode and a scan tool will show requested gear / position of the shifter. I'm also wondering if , in normal operation , when the shifter is placed in manual mode the Sport or Normal lights go out. Try a manual shift mode when everything is working properly or when the problem occurrs.
Quote:
Originally Posted by l_turn9
I had bought an expensive battery to move it around while I did the t'shooting and repairs. It's an inexpensive battery which drains after 3 or 4 days if we don't start it or charge it frequently. I was wondering if installing the correct battery would fix the shifting problem?
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Battery size isn't a problem if it goes down after 3 - 4 days, a larger battery might only get you another day and won't solve the problem. You could run the car on a lawn tractor sized battery and once the engine was running , not have a problem.
Quote:
Originally Posted by l_turn9
The car really comes alive electronically when I charge the battery for a couple of days and everything seems to work: Navigation, Cruise Control, and all the other electronic goodies which don't usually work. But all the electronics drain the battery (too small) and we lose all that stuff.
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You really need a scan tool and to check voltage of the charging system. Given all of these problems are occurring there is a common failure point. I've seen alternators have a shorted diode cause battery drain , apply electrical noise to the system that causes all sorts of problems.
Above all, diagnose and don't randomly throw parts at the car.
Quote:
Originally Posted by l_turn9
I wasn't making the connection between the amount of charge and the AT's functioning until recently.
Any ideas if I might be right?
TIA,
Larry
2006 MB E350 AWD
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If the alternator is working properly and the engine running, a drained battery will recharge and the car operate properly while it is being charged.