My mother's 2001 Sonata had a check engine light. I hooked up my scan tool and found P0118 and P0720. I purchased a new coolant temp sensor and new Output speed sensor and tonight I changed them both. I erased the codes and immediately the P0118 code came back.

She drove to the gas station a mile away and said the check engine light came back on and the car got stuck in 2nd gear and when it shifted it shifted hard enough to squeel the tires. Now both codes are back along with P1529.

Now what?

note** I did not disconnect the battery before changing the sensors which was probably stupid.

 

Was the trans fluid changed on time? Bet it's smelly and old, isn't it?
You could try changing the trans fluid, and disconnect the neg battery cable to reset the adaptive learning on the TCM.

 

thanks for the reply. I'll check the oil when I get home. Kid at hyundai parts counter mentioned it as well.

 

I have a tiburon with the same codes. The dealer just changed the input and output speed sensors, so far so good.

When the car went into the transmission safe mode it goes into 3rd gear. It seems to even start from a stop in that gear because starting acceleration is very poor and then it kicks in rapidly, sort of like a slipping transmission.

I rear ended a car because it took me by suprise. Is that surge normal?