My 01 996 turbo keeps throwing 2 O2 codes. 1128 & 1130. My scan tool doesn't give me much info on either and I don't have access to shop manuals at the moment. Can somebody please tell me what these codes are, more specifically. I am guessing the heaters as this is a known problem with these...but it may be reading out of range as it seems to running a bit rich at idle. ?? Only engine mods at the moment are a protomotive exhaust...

The problem is intermittent, and takes about 200 miles of driving to come back on...and seems to come on at idle after a hard run.

thanks in advance for any help...
dave w