OBDII Code P0432 Question

[rubicontrail]

I have a 2001 Jeep Cherokee with the 4.0L engine. Last night she through a MIL.

I put the OBDII scanner on her and it said P0432 MAIN CATALYST BELOW THRESHOLD (BANK 2)

I pulled up the enhanced diagnostics and the voltages of the Bank 2 O2 sensors seem to be tracking each other. So does that mean that the Bank 2 mini catalytic converter is toast?

This vehicle has about 150,000 miles on it and all the cats and rest of the exhaust system is original so I wouldn't be surprised if it's all starting to go.

If it is gone is it something that needs to be fixed immediately or am I good for awhile (it isn't due for emissions check until September)?

[ademster]

it will need a new cat 90% of the time that is the problem.

[ademster]

But the question is. What caused the catalytic converter to die?

Do you have a misfire? Running rich? THe number one cause of the catalytic converter is Unburned raw fuel entering the catalytic converter which causes the converter to overheat.

Inspect the whole exhaust system, for heat discoloration, and leaks.

also pull the post o2 sensor and inspect it, it maybe contaminated. Do not use any solvent type cleaners on the o2 sensor.

[rubicontrail]

Well was having issues with failing engine bearings. Those have been replaced and the engine is running much smoother.

Can't the cats just die from age though... I mean it is now reached twice it's warranty and the whole exhaust is getting pretty beat (keep in mind this Jeep has seen plenty of mud and some winter road salt being it started it's life on the East Coast).

If the O2 sensors for Bank 2 are both tracking with the same voltage wouldn't that mean they were still functioning (not really sure I understand how the O2 sensors work)? :-)

Also, this vehicle has three cats. Two mini ones right below the exhaust header and then the normal one. I think that is the CA Emissions design and for 2001 that they actually used this in all the US Cherokees. So, if it is that bank 2 one... then I have to replace to the exhaust header :-(.

[ademster]

the o2 sensors switch from .65volts to .800volts they should be switch back and forth

if it is bank two then it is the cat that is down near the muffler, but some of of them are both intergrated to the exhaust manifold. so then yes the manifold will need to be replaced.


and yes the honeycomb mesh inside the cat in time does fall apart, and also cause failure. to where it doesnt get red hot.
a catalytic converter is basically an oven. it get super red hot inside which will burn the raw fuel that the engine doesn't burn. if it isnt getting to the proper temps inside, the o2 sensor will notice and throw the code.

[rubicontrail]

I am not going to damage the Jeep from driving it with this issue, right?

Also, does anyone have any good suggestions for exhaust headers, muffler, etc. for a 2001 XJ? All the ones on Quadratec seem to only go up to the 2000 year. I want it to remain pretty quiet (makes enough rattles and squeaks, etc.... don't need any additional noise).

[ademster]

No it wont, but your fuel milage and performance will deteriorate.

[rubicontrail]

Yeah, I plan on fixing it... just can't immediately as I just dropped money into it fixing the engine bearing issue.

[ademster]

I hear ya.


let me know if you need to have someone do it, I can beat any shop prices, on installation minus the parts.

If you buy the parts I can do the work.

[rubicontrail]

Will let you know. Might just throw a wrenching party.

I'm still trying to figure out what all parts I need as the 2001s seem to have had a different setup than the 2000s. :-(