P0420 Code On 1996 Plymouth Vayager Minivan

I'm getting a code P0420 ( Catalyst Efficiency Below Threshold) on my 1996
Plymouth Voyage Minivan. It has 160,000 miles with a 3.0 Engine. I was able
to clear the "Check Engine Soon Light" with my code reader, but it keeps
coming back after a couple of days. Now it stays on constantly, but can be
cleared. I replace both the before and after oxygen sensors and the EGR valve,
which included cleaning the EGR valve tube. The timing belt and water pump
was replaced a year ago. The car runs good with an occasional lifter ticking
(but that’s another issue for later). Any ideas?

 

I'm getting a code P0420 ( Catalyst Efficiency Below Threshold)
( Catalyst Efficiency Below Threshold)
( Catalyst Efficiency Below)
( Catalyst Efficiency)
( Catalyst)

I don't have any ideas, sorry.

 

It most likely needs a catalyst. The PCM uses a complex algorithm that
compares both half cycles and slope, or rate of change, of the Oxygen sensor
signals, comparing the front sensor to the rear one to determine if the
catalyst is working properly.

Oil consumption is common on these engines, and this will poison a catalyst
over time.

I would highly recommend an OEM catalyst. Aftermarket replacements, even
direct fit versions, generally have MUCH lower standards for function and
may only work for a short time if at all. 1996 is the first full year the
catalyst needed to be monitored, per OBD-II regulations.

Tom Showers
Certified/Specialist Chrysler Technician
ASE CMAT, L1
Sawyer Motors
Saugerties, NY

 

The catalytic converter is bad. Replace it.

Glenn Beasley
Chrysler Tech

 

chances are you need a new cat. converter

 

Thanks guys. I replace the converter and cleared the code and it has not come
back.