Catalytic Converter needs replacing after a year on 1999 Infiniti QX4

My 1999 Infinity went off into a ditch in 4 feet of water. Had insurance company repair it, after the mechanic had it for three weeks - got it back and check engine light was on. Now brought it to another mechanic they say its the catalytic converter-un related to claim.
I just had a new catalytic conv put in over a year ago. Can the damage to catalytic converter be related to being submerged in 4 ft of water?

Asked by for the 1999 Infiniti QX4
The catalitic converter could be damaged if it was full of water. If the car set for a while, I'd expect the exhaust to have water in it.
Thank you Superbob, We picked up our car from dealer and we are going to get a local mechanic to look at our car. It seems to me that after sinking into a ditch of water, the exhaust was under water as well and we saw the water draing out.
1 more answer , 1 more comment
First off... you need to make sure that the catalytic converter that was installed was made by Infiniti. We have found that non-OE catalytic converter will ofter fail and set the check engine light.

Secondly, check the oxygen sensor connectors and look for corrosion on the connectors, that may be causing the wrong signals to get back to the computer.

Good Luck! - A+ Japanese Auto Repair, San Carlos CA 94070
Thank you Eric, we will ask the mechanic who installed it and make sure. It was expensive enough, I hope it was an infinity part.
Qualified Local Infiniti Shops
Qualified Infiniti Shops For This Repair
780 Industrial Rd
San Carlos
Technical Ability
Tools & Equipment
Customer Service
Customer Amenities
(650) 482-8094