Can anyone tell me what "3 way cat damage" refers to in these codes.
544 Misfire more than one cylinder, three way cat damage
545 Misfire at least one cylinder, three way cat damage

the codes are from a 95 Volvo 850 turbo, thanks for the help

 

see attached pdf's

 

850s have two O2 sensors one before and one after the cat. The computer can compare values and also listen for misfires via the knock sensors. the codes reflect the combination of error events. Could be your cat, could be an ignition or vacuum issue, could be an O2 sensor going out... Mixture issues (ie lean/rich) can throw a range of codes -even bad gas etc.

 

To clarify, these two codes include the term "cat damage" to alert you that the misfiring was significant enough to cause cat damage. The cat will overheat quite a lot if enough unburned fuel gets to it and reacts there.

This is not a code telling you that cat damage was detected. it is misfires that have been detected.

A "three way cat" burns hydrocarbons, converts nitrogen oxides to nitrogen, and burns CO to CO2. Three reactions are going on. The fact that you have a three way cat is not involved in the problem that was detected, it's just something that somebody typed into a database.