I have a 2001 hyundai accent, recently why'll driving on the highway the transmission shifts in and out of overdrive,,but only when driving between 80 and 100 kmh ,,after about 10 minutes it seems to be ok ,,but it happens everytime i first get on the highway. i have changed the transmission filter and fluid. i have also replaced the TPS,spark plug cables and plugs. and also repaired the wire problem located in the shifter compartment. There is no codes showing up at all and i have run out of ideas as to what may be the cause.i purchased this car brand new in 2000 and have been very satisfied with it. so as i am the only owner i know it has been well maintained and never been abused or neglected and i would really like to figure this out before it causes any problems and costs to much to repair.

 

i would check at www.hmaservice.com to see if there are any TSB's regarding your transmission and the transmission control module (TCM). see if there are any software updates for it, you'll need to see a dealer to get that checked/done but it should be cheap.

those older auto tranmissions coupled on the 1.5L are kinda flaky at best....

 

well to answer my own question.....as it turns out i needed a transmission fluid temperature sensor.....the dealer ship was telling me i needed a torque converter..or new transmission.......but i finallyy got a code to show up and thats all i needed....70 bucks and now its runningg tip top again,,alot better than the 1700 bucks they quoted me...ig you have trouble with your tranning shfting try looking at this first...hope this helps someone in the future.

 

hey thats great news! also why i like doing my own work, its too easy for shops to bill you for something you don't need. torque converter doesn't sound right for your problem - i would have actually guessed a solenoid, but hard to say without that code u got. great work!

 

I have a vary similar problem and I checked for a trans temp sensor and don't have one. My car will not go into high gear intermittently. So at 80km/h, I am revving at 3000rpm. If I pull over, put the trans in park, shut off the engine, then start going again, the trans will often run through the gears fine. sometimes I will be driving on flat ground and it will drop out of high gear and stay there. Same thing if I pull over.
A new development today is that the car feels like it is just staying in 3rd or 4th gear. So it is sluggish to start and revs on the top. I got a po734 out of it. any ideas?

 

What car, year, engine?

P0734 = A/T 4th gear ratio problem

Have the Pluse Generator checked by a transmission shop.

 

01 Accent 1.6L put a pulse generator in and it made no difference. there is also a p1529 engine code. Are there any other ideas.
thanks

 

Accent with output speed sensor code is an inspect sensor with Ohm meter, if in spec, re-program TCM..

If sensor is out of spec, replace generator set,,, AND reprogram TCM

You likely failed to re-program the TCM,,, it is program #18 I think... it'll come up on GDS if applicable to be done in the ECU UPGRADE mode..

OOOOOP's ,,,,, flash drive at work in my car with GDS screen shot for the program (I drove customer car home for GDS & flight record of data if concern shows up).. I try to post screen shot tomorrow..

Disregard the 1529, it is a request from the TCM to the PCM to illuminate the MIL... It (1529) will clear when the original TCM fault is repaired and cleared.

 

if you can't reprogram the TCM (most of us can't without the necessary expensive tool) see a dealer or a good transmission shop for that. you can instruct them to do ONLY that if you want. i have had to do that myself in the past.