Originally Posted by dell

I bought an Elantra 2001 with 121,000 miles, 3 months back.

2 weeks back, while doing freeways the tranny jerks and goes to third gear.This was very rare. once i restart the engine, the check light goes off and the car is fine.

I got all the fluids refilled and found that tranny was short of 2 quarts. After refilling, after 1 week, the problem became more rampant on freeways, the check engine light used to stay on for 2-3 days.

I took it to the aamco, when the engine light is off, they gave me two codes
P0715
and
1529.

So, I bought the input speed sensor and got replaced at local garrage. They didn't reset the battery.

yesterday while doing freeway, the problem reappeared and I restarted the the engine, the check light is gone, the car was fine and i also did a 30 mile drive on freeway.

How important is it to reset the battery and for how long i need to disconnect the battery.
Considering the miles on tranny, can there be any hidden problems?