I recently used a diagnostic reader (vgate) on my 92 GT, and it worked fine. It showed a few error codes which I then sorted and erased. 

For some reason now whenever I try to read the error codes it'll only show

If I then clear the error codes and try again it will say that there are no error codes. 

To me it seems to be talking to the ecu ok but not reading the codes properly like it originally did!

Anybody have any ideas what's going on?

Thanks

Looks to me like it is giving you a code, 00518, but the scanner hasn't been programmed with what that code means. A quick search suggests that code relates to the throttle position sensor.

Cheers mate,

i did have a look for the code but stupidly only searched for 518 not 00518 and it didn't come back with any results!

 

Some codes are generic and some are codes specific to the manufacturer which will mean you have to determine them with info from that manufacturers data.