Why is it that some scanners i.e. I have a Autel Maxiscan MS509 will not detect all codes

Question

i.e. I know I have a Electronic Throttle Control issue since the ETC light is flashing!? Help appreciated

The light tends to go away once the engine has warmed up and I restart the engine suggesting a temperature related problem. Any ideas which sensor could be at fault?

Plus I would like to get hold of a scanner that can read all my Jeeps codes, is it the fact that some scanners read only generic codes whilst different car manufacturers write software for their own codes??

Yuri