2003 Liberty Catalytic Converters P0420

[libertybob]

My 2003 Liberty 4x4 3.7L is intermittently setting code P0420, cat efficiency low on bank 1. 2003 Liberty's changed cat setup effective 2/14/03.

My Liberty was built in June 2003 and has the driver side cat welded into the crossover pipe with the passenger cat bolted onto the crossover pipe and with a third non-monitored cat welded into the crossover pipe just before the flange bolted to the muffler. This was a 6 month part as the cats and crossover pipe changed again for 2004.

The 2002 and early 2003 cats and crossover pipe were the same up to 2/14/03. The setup was that the driver side & passenger side cats were both bolted to the crossover pipe which had a third non-monitored (?) cat just before the flange that bolts to the muffler.

Can the 2002/2003 up to 2/14/03 cats and crossover pipe be bolted in to replace the later (after 2/14/03) cats and crossover pipe? I can source a low mileage 2002 setup and want to know if it will perform satisfactorily with the computer and emissions systems. Or must the 6 month cat setup after 2/14/03 be replaced with exact replacement parts? I would prefer the more common 2002/early 2003 setup if it will work in my Liberty.

Has anyone made this switch? Experts, please advise....

 

[TwoBobsKJ]

When I bought my ****** skid plate for my '03 from JeepinByAl I had to ship the first skid back because it wouldn't fit around the downpipe/crosspipe. Wasn't Marlin's fault because of the very thing you're running into - Jeep decided to make a bunch of changes for no apparent reason :shrug:

As far as I know - and place as much or little weight as you want on my knowledge - you'll be able to use the "modular" cat & crosspipe system from the early '03s and '04s. Your changeover version is the red-headed stepchild it would appear but operationally there is no difference in how info is transmitted to the vehicle computer; the pipe layout is mechanically but not electronically different.

I've replaced the cats in mine and though they are a pain to R&R due to the V-clamp that holds the cats to the exhaust manifolds it's better than the one-piece design you're unfortunately dealing with.

Bob