2006 4runner P0420 202k miles
Check engine light came on a couple weeks ago, it’s always p0420 even after I replaced both o2 sensors on that side. Should I replace the cat asap to avoid damaging the engine?
If the catalytic converter is blocking up ( it can be pressure tested to conform this) something is going on upstream of the CAT to cause the problem, usually, running too rich or burning oil. You need to find the cause of the problem. If you don't do that, a new and very expensive CAT will just go bad quickly.
@doc thank you, that is great information!
separate problem…seems like it won’t shift into 4th gear after using 4WD for the first time last weekend. Is it possible that messed with something? What could I try to check to fix it? No error codes yet.
You never said what engine or transmission you had.
Sorry about that, it's the 4.0L v6. SR5 4WD. Automatic 5spd transmission.
Correction...just scanned with BlueDriver and have a pending P0776 code.