I've been popping P0420 codes recently, and also experiencing a few stalls (no code). I've done a lot of searching and believe that my cat is not likely the problem.
Reference this thread.
Per TSB. Some causes of P0420
Ã?â??Ã?· Malfunctioning ECT/CHT
Ã?â??Ã?· High fuel pressure
Ã?â??Ã?· Damaged exhaust manifold
Ã?â??Ã?· Cylinder misfiring
Ã?â??Ã?· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
Ã?â??Ã?· Damaged exhaust system pipe
Ã?â??Ã?· Damaged muffler/tailpipe assembly
Ã?â??Ã?· Retarded spark timing
Damaged Catalytic Converter:
Ã?â??Ã?· Use of leaded fuel
Ã?â??Ã?· Oil contamination/consumption
Ã?â??Ã?· Silicone contamination (sealants/cleaners)
I'm determining a game plan and want some grey-hairs to advise. I think I'll first run down the list above, specifically focusing on the checking for high FP & bad ECT.
If these check out ok, I plan on cleaning the IAC, as it's been 4 yrs and ~63K since it's been installed as new.
If I get this far without finding it, then things get fuzzy as to what to check next. Any suggestions from here (or my plan in general)?
PS. My plugs/wires a 6 months old, and I'm not experiencing any misfires, so I suspect my ignition & coil are ok.
