Management light on after a period of a week after code clearance. No running symptoms!

P0422 Catalyst efficiency below threshold bank 1

Check for induction & exhaust leaks. Non found!
Checked the EVAP canister for fuel contamination build up, all seems o.k!

Both upstream & downstream oxygen sensors seem to be functioning good & reacting well!

Only thing I can see that might be causing the code is high short term fuel trim around +25 at idle. Long term seems to counter at around -8. After a short run all fuel trims fall back good.

Exhaust emission are fantastic so no pussy failure there.

Have checked the wiring loom at the ECM as they are common fault, everything lovely.

The only change to this vehicle was it recently had a timing belt before this code raised it's ugly head!

Only things that I can think of that relate to this fault code are Exhaust or intake leaks or bad pussy!

Vehicle runs great.