O/T Leagcy CEL CAT ECU

[svx_commuter]

O/T Legacy 2.5 GT limited 90k miles

A friend of mine has a problem..........

The check engine light stays on. The dealer says it's the catalytic converter and a knock sensor. That's $650 for thje car. The car has an extended warranty to 100K but dealers says Cat is not covered.

At around 70k miles the ECU was replaced due to engine knocking. This was done on warranty.

Do you think a case could be made with SOA that the faulty ECU ruined the CAT? The dealer has agreed to 50/50 good will replacement based on this argument.