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?

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fab4 via CarKB.com
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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.

Reply to
bllsht

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

Reply to
Tom Showers

The catalytic converter is bad. Replace it.

Glenn Beasley Chrysler Tech

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maxpower

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mr158912

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fab4 via CarKB.com

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