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2001 Automatic Transmission Shifting Erratically

4K views 6 replies 5 participants last post by  danielson3 
#1 ·
i have a 2001 elantra with 136k. the automatic transmission (which otherwise shifts very smoothly and shows no sign of problems) shifts suddenly and erratically when i'm driving at a constant speed. i'll be traveling along (speed doesn't matter), and it will suddenly downshift, then upshift, then downshift, etc. this started off being very occasional, but now it randomly shifts every 5-10 seconds.

i've changed and checked the fluid, and tried replacing the Input Speed Sensor and the Output Speed sensor...that didn't fix it. it also does not blow a check engine code. i'm convinced there must be a sensor somewhere that is faulty. it really seems as though the transmission is electronically confused.

any help is greatly appreciated.
 
#3 ·
You need to access the TCM and see if any codes hiding in there.
 
#6 ·
QUOTE (ghetto3jon @ May 14 2011, 01:02 AM) index.php?act=findpost&pid=445283
i have a 2001 elantra with 136k. the automatic transmission (which otherwise shifts very smoothly and shows no sign of problems) shifts suddenly and erratically when i'm driving at a constant speed. i'll be traveling along (speed doesn't matter), and it will suddenly downshift, then upshift, then downshift, etc. this started off being very occasional, but now it randomly shifts every 5-10 seconds.

i've changed and checked the fluid, and tried replacing the Input Speed Sensor and the Output Speed sensor...that didn't fix it. it also does not blow a check engine code. i'm convinced there must be a sensor somewhere that is faulty. it really seems as though the transmission is electronically confused.

any help is greatly appreciated.

sounds like the transmission range sensor to me i had the same problem and it turned out it was that replaced it and it got a lot better and i did the speed sensors as well mine still does the erratic shifting here and there but i havent had the chance to adjust the transmission switch yet be sure to when u change out the sensors to get the codes wiped then drive 50 miles then check for codes again..
 
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