Originally posted by Tony2005:
Originally posted by projectSHO89:
...Plugged cats usually cause other problems, not efficiency codes.
...


Correct.

Here is something from the TSB (in our own backyard for documentation).

"P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold.

�· Malfunctioning ECT/CHT
�· High fuel pressure
�· Damaged exhaust manifold
�· Cylinder misfiring
�· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
�· Damaged exhaust system pipe
�· Damaged muffler/tailpipe assembly
�· Retarded spark timing

Damaged Catalytic Converter:
�· Use of leaded fuel
�· Oil contamination/consumption
�· Silicone contamination (sealants/cleaners)"

It appears, if the P0420/P0430 is caused by the top eight items, yes, the engine is already running rich or lean and the engine is sent to the limp mode (I am correct here). If it is caused by the bottom three items, it should not run in the limp mode until it causes other issues. So the P0420/P0430 codes does not necessarily cause the engine to run in a limp mode immediately all the time (you are correct here).



Don't forget that many times (I even think most times) that cat effeciency codes on a Duratec Contour is a flase positive. There may not really be anything wrong. I have p[osted on that in the past.

Jim Johnson 98 SVT 03 Escape Limited