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Tim Mohr
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Grand Caravan: 2005 Grand Caravan, 3.3 engine, R code on VIN.

Customer Question

2005 Grand Caravan, 3.3 engine, R code on VIN. 200k miles. Has a PO420 cat code. Code was there when I bought car with 150k miles. Replaced cat with aftermarket unit. LIL stayed off for three months, then on all the time, same PO420 code. O2 sensors replaced three times, no change. I have also noticed that when the car in run for 200 miles, the engine idles rough, even in Park. It also feels slightly hoppy at 70mph, like tires out of balance. Could I be looking at weak fuel injectors, not weak enough to throw a code. Chrysler mechanic says all systems check out on a computer, replace the cat. Getting might frustrated, car runs fine otherwise, uses a quart of oil every 4 to 5000 miles. Any suggestions?
Submitted: 2 years ago.
Category: Dodge
Expert:  Tim Mohr replied 2 years ago.
Hi, my name is***** this will not be fuel injectors, the P0420 can only be caused by a cat converter not cleaning up the exhaust, and we see this alot with aftermarket cats, they are not efficient enough to work on the 1996 and up OBDII systems, we always use factory cats on these to avoid this problem, if the down stream o2 sensors have been replaced, then it can only be a bad cat,Tim

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