The EPC light from my Audi TT 2004 was turned on, after that the Check engine light also was on. Now the EPC light disapear but the check engine remain on, do you know whats going on?

You have a vac om leak or the idle valve stake ,all the best.

The hissing noise is normal but it seems you have to either check the wire going to the ckp sensor or change the sensor.

If you mean ESP, or Audi's traction control, then follow this link:

http://www.audiforums.com/forum/audi-tt-7/esp-light-wont-turn-off-81683/

If you mean EPC, then sorry, I cannot help you there.

I recommend asking this question at an Audi forum or searching for the answer in their archives.

http://forums.fourtitude.com/
http://www.audizine.com/

if vechicle getting spark and fuel.timing could be off due to a worn timing belt.i would do a compression test see what condition the engine is in.

First of all you need to access the Engine Control Module (ECM) using suitable diagnostic equipment connected to the data link connector of the car, in order to pull out all DTC's memored. DTC = Diagnostic Trouble Code. Then you will bu full informed about the root cause of the problem, and you will be able to repair & replace bad pieces and reset the ECM. Then the engine light & EPC (Electronic Pedal Control) yellow light will turn OFF.

The check engine light:


The check engine light & EPC light:

I am having the same problem on my Audi A4 2004 FSI, lose power whilst driving at speed with the EPC light coming on. Looks like a design fault of some kind with Audi petrol engins, have read a few forums about this but no clear straight answer. Check the link below:

http://www.audi-forums.com/b6-forum/37371-a4-fsi-epc-light-power-loss.html

This is some kind of sensor that will need changing. Mine cost me around £60

You will need a scan tool, or just drive the car and if it was due to battery once the computer finishes running its diagnose checks it will turn light off, this may take a week and some driving around. you could also have the computer scanned to see what code is stored and see if its due to the battery.

2005??? dealer only encrypted software to stop general garages from doing the work .

I would suggest you check oil levels etc. Generally these cars suffer from the air mass meter / air sensor problems aswell as coil problems too. Did you ever get a solution to the problem?