Code help... P0432

I just got this code on my new to me 2001 XJ. The OBDII code was

P0432 (M) 1/2 Catalytic Converter Efficiency Catalyst 2/1 efficiency below required level.

Can anyone help me w/this code and what exactly it means? Does that mean one of my pre-cats is bad or clogged perhaps?

Thanks all.

From a Google search (great place to go with codes).
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Fault Code Definition

Code P0432 indicates that the Bank 2 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

Check Engine Light will illuminate
In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0432 Code:

*Defective Catalytic Converter
*Engine misfires have damaged the Catalytic Converter
*Internal engine damage resulting in high oil consumption and/or a leaking Head Gasket has damaged the Catalytic Converter

Common Misdiagnoses"

*Oxygen Sensor(s) are replaced when the real problem is a damaged Catalyst
*Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
*Catalyst is replaced when a misfiring engine is the real problem

Start by checking the wiring to the rear O2 sensors. It could be a bad cat converter or a bad rear O2 sensor. In any case, this won't prevent the engine from running correctly. It will however flag you during an emissions check as the engine computer thinks it's emissions are too high.

I thought that the cats efficiency was calculated by comparing the Co/No levels going in and then coming out of the cat as read by the pre & post cat 02 sensors? Testing all the sensors involved would be logical first step. If sensors check out then yes pulling off the precats would be my next move to see if they are look damaged, clogged or burn out.

If one or more of the cats are damaged then determining why they were damaged will bring you closer to understanding what the underlying root cause could be. Is it too much gas getting in the exhaust for various reasons or is it just that the cat had naturally worn out from a longer than expected service life? My original minicats are 11 years and has 170,000 miles on them so yeah they can/will last a long time but not forever eventually they like everything else fail. Taking them off and having a good look at them should give you a good idea of how well they are doing (are they nice and clean inside, can see through both screens still, can you see the catalyst material inside, are there any rattles from broken catalyst material or torn, missing or damaged screens) or you might find the worst case scenario (they're completely burnt out, melted inside and nothing more than hollow tubes) Either way finding the root cause (bad leaking fuel injectors, malfunctioning fuel pres. regulator, poorly maintained basic tune up equipment, lack of synchronization between valve and ignition timing, various defective or malfuntioning sensors and poor connections will be the key to it not happening again.

Thanks for the tips and info. This '01 is one I just picked up and it was a service vehicle for most of its life. Only 112K miles on it... but I have no idea how hard those miles were. Looks really clean, but I haven't been able to go thru it yet for tune-up parts. Planning to pull the plugs and give those a look and replace this weekend hopefully. Air filter is as-new, no oil leaks and just changed that out so all it good there.

I cleared the code after pulling it and it hasn't come back for about 100 miles so far... but I'm still going to keep looking for what could have caused it. I doubt it'll just go away.

robsjeepxj said:

I thought that the cats efficiency was calculated by comparing the Co/No levels going in and then coming out of the cat as read by the pre & post cat 02 sensors?

Click to expand...

The O2 sensors used are almost on/off switches, reading either lean or rich. The engine computer controls the air/fuel mixture to get the pre-cat O2 sensor oscillating between rich and lean. It looks to see that the post-cat sensor is saying lean (all the O2 is burned up) and occasionally saying rich such as during startup when the cat isn't warm enough to do anything.

Bringing this back up...

I replaced the Post-Cat O2 sensor a month or so back... Cleared the code and it keeps coming back. I've been on the lookout for a replacement Cat-Converter, but haven't taken the plunge on buying a new one yet.

I was thinking back to my Mustang days... and you could install a MIL Eliminator to fool the vehicle into thinking the Cat was still present (after installing an Offroad X or H-pipe). Would it be possible to build a MIL Eliminator in order to fool my XJ so I don't have to keep looking at the light. Hard to ignore, and worse if it's actually hiding a legitimate problem and I just think it's the P0432...