My sons G6E did the same thing 2 weeks after buying it s/h , no communication codes ect with the scantool but we couldnt clear the codes. Anyway long story short took it to our w/shop left it overnight checked battery voltage next day and it was low 12.2v. Replaced the battery and all is fine with all hard codes gone.Has been good for 5 months but other probs are arising now that I have yet to sort out.