Ck Engine light & tachometer to 0 problem

After 2 weeks in the dealership, they cannot find out why the ck engine light flashes, tachometer goes to almost 0 , and momentarily loses power while driving. Sometimes stalls at stops, but starts right up with key. Has new battery and all new ground wires. They tried replacing the PCM module...still had symptoms. Any ideas?...they are stumped...no codes registered. Calling in a Hyundai guru>

i have a similar problem 2001 elantra 62000 miles have dtc p0081 and a couple other undocumented codes mine will just cut out and the check engine light will flicker then start right back up

did u ever find a fix for your car i am having the same problem and can not seem to pinpoint what is wrong thank you for your time

CAM sensor fixed the problem $35.00 plus $10.00 labor thru local garage.....It has been running fine since this fix in March 2007