Had that problem to a while back, took it in for a strange noise problem, not sure if it was the moose or not, and then a day or two later the engine light came on. Took it back a week later and got brand new cats! At least it kinda worked out for me good luck in finding what's wrong. My guess would be to coolant flush/brake work too. Who knows maybe a not so good mechanic knocked somehting loose when they were working on it.
