Hyundai Repair: Hyundai Elantra 2001 acceleration problem, haynes repair manual, hyundai elantra

Question
Hello Onder,

On my 2001 Elantra the engine light comes on as soon as I start the car.  The acceleration (hesitation) problem start in about 10 minutes of driving (probably when the engine gets to a certain temperature). The codes are P0456, P0715, P1166, and P1529. Upon doing some research and checking in Haynes Repair Manual, the best I can understand is P0715 is the speed sensor malfunction and P1166 is Oxygen sensor malfunction. P0456 seems to be EVAP emission control system leak although very small.  P1529 seems to be a request from
TCU to ECM to turn on the engine light. Here are my questions.

Do I have to replace the Oxygen and the Speed sensor because they are malfunctioning?  Is it possible that they are malfunctioning because of some other problem?  How can I determine the real problem?

I would appreciate your opinion on this issue. Hope to hear from you soon. Thank you.

Have a great day!

Anies

Answer
Hi Anies,
You should replace the related upper O2 sensor  and both input and output speed sensors on the transmission. I think this will take care of your problem. For the evap leak, it is usually caused by a loose gas cap. Check the gas cap and make sure it is tight before you erase the codes and test drive.