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-   -   P0420 Code? (http://www.jeepgarage.org/f203/p0420-code-15946.html)

rojpon74 12-06-2010 11:09 AM

P0420 Code?
 
Hi Everyone,

My 2002 WJ Overland with 4.7L HO engine has the California/50-State emissions system (4 oxygen sensors, 2 mini catalytic converters before the main convertor, no oxygen sensor after the main converter).

I'm getting a P0420 DTC, which according to the service manual and wjjeeps.com translates to "Catalyst System Efficiency Below Threshold (Bank 1)".

Question: which catalytic converter is this referring to? I'm assuming it's one of the mini converters since it refers to "Bank 1".

Thanks everyone for your help! :thumbsup:

Frango100 12-06-2010 01:56 PM

Re: P0420 Code?
 
I'm not an expert on O2 sensors, but because the PCM is looking to the O2 level before and after the mini converter, it can only see the performance of that particular mini converter. How you can ever know if the main converter is working ok, i have no idea.

2005JGC 12-06-2010 02:59 PM

Re: P0420 Code?
 
bank 1 is whatever side of the engine the #1 cylinder is on... on the 4.7 its on the drivers side.

possible causes:

INTERMITTENT CONDITION
VISUALLY INSPECT CATALYTIC CONVERTER
EXHAUST LEAK
ENGINE MECHANICAL PROBLEM
UPSTREAM O2 SENSOR OLDER THAN DOWNSTREAM O2 SENSOR
CATALYTIC CONVERTER


rojpon74 12-06-2010 03:45 PM

Re: P0420 Code?
 
Thanks. What would be the symptoms of an exhaust leak? I just had the heads rebuilit a month ago and they had to pull the exhaust manifolds as part of the removal/installation process. I also got a P0155 code a week ago...seemed to be an anomoly since it hasn't come back after I erased it with my code scanner.

Quote:

Originally Posted by 2005JGC (Post 312857)
bank 1 is whatever side of the engine the #1 cylinder is on... on the 4.7 its on the drivers side.

possible causes:

INTERMITTENT CONDITION
VISUALLY INSPECT CATALYTIC CONVERTER
EXHAUST LEAK
ENGINE MECHANICAL PROBLEM
UPSTREAM O2 SENSOR OLDER THAN DOWNSTREAM O2 SENSOR

CATALYTIC CONVERTER



2005JGC 12-06-2010 04:55 PM

Re: P0420 Code?
 
P0155 is an O2 sensor heater fault code... but its a 2/1 code (bank 2 upstream) so more than likely not related to your current P0420 code.

4.7's regularly break exhaust studs (the back 2) and you would know by a ticking noise while the vehicle is running. Sometimes worse when its cold, if it gets really bad it will be all the time. if you have had a leak for a while you can see soot buildup around the leak.

Why was the head rebuilt? misfires will quickly meltdown a cat (why the mil flashes), foreign material getting into the exhaust can kill it too.

rojpon74 12-06-2010 10:03 PM

Re: P0420 Code?
 
Thanks very much for the information. I'll take a look at the exhaust manifold and studs.

Heads were rebuilt due to warped heads and a couple of burned valves. Problems were centered on the right hand (passenger side) head but did the left side too for good measure. The engine had close to 200k miles when the heads were rebuilt.

Quote:

Originally Posted by 2005JGC (Post 312907)
P0155 is an O2 sensor heater fault code... but its a 2/1 code (bank 2 upstream) so more than likely not related to your current P0420 code.

4.7's regularly break exhaust studs (the back 2) and you would know by a ticking noise while the vehicle is running. Sometimes worse when its cold, if it gets really bad it will be all the time. if you have had a leak for a while you can see soot buildup around the leak.

Why was the head rebuilt? misfires will quickly meltdown a cat (why the mil flashes), foreign material getting into the exhaust can kill it too.


2005JGC 12-06-2010 11:11 PM

Re: P0420 Code?
 
btw a broken stud is VERY easy to locate... the studs that mount to the heat shield are what break, so just get your fingers on the back of the heat shield and try (gently) to pull it away from the head, you will know if its broken because it will move... otherwise its solidly mounted and should not budge.


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