Header says it all 99 XJ8 , cant clear codes , curious what module stores them , Thank You

 

Depends on the code e.g. ABS codes will be in ABS module and so on. The only codes a typical tool can read are in the PCM and the tool can clear them. Of course the fault may still be there and can immediately re-flag so may look like the tool failed. Fix the fault....

The OBD idea is that you always carry out a fix before a clear. Codes self-clear when fault fixed so strictly you don't need to clear the code.