So I'm helping a friend with his 2005 PT Cruiser. He recently had the timing belt replaced, and ever since the speedometer hasn't worked and he has a P0501 error code. The guy who did the work replaced the transmission input and output speed sensors in an attempt to fix it, it's still dead. Because the transmission is shifting fine I feel like its not a sensor issue. Also I put my Snap-On scanner on it and it has input and output speed readings, but no vehicle speed reading. Vehicle is also running rough and sometimes stalls when coming to a stop similar to having a stuck EGR valve. Ive gone over the motor looking for connectors unplugged or damaged harness and found nothing obvious. reading online turned up nothing as the speedometer not working it usually the output sensor, and includes shifting problems which I am not experiencing. Any help figuring this out would be appreciated RE'