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Old 10-05-2008, 06:33 PM Thread Starter
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Emissions code

So while driving home today after a family reunion the check engine light came on.

I checked the code and it was a p0420. After a little searching it appears to be "420 The catalyst seems inefficient (#1)".

Has anyone else had this code?

I guess I could use this as a reason to get that exhaust upgrade I want
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Old 10-05-2008, 08:36 PM
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Quote:
Originally Posted by jcoulter View Post
So while driving home today after a family reunion the check engine light came on.

I checked the code and it was a p0420. After a little searching it appears to be "420 The catalyst seems inefficient (#1)".

Has anyone else had this code?

I guess I could use this as a reason to get that exhaust upgrade I want
More often than not that one will be an o2 sensor.
The exaust is sampled prior to and after the cat by the o2's.
If the rear o2 sees minimal difference from the front o2 it is interpeted as a ineffective catalyst and sets a code.
More often than not, the rear o2 is becoming unable to get good sample info to the E.C.M.
It will fall under the Emission warranty.

Good luck,
.....Rob
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Old 10-06-2008, 12:51 PM Thread Starter
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If I read the warranty correctly the only items covered after the 3yr/36,000 are the catalytic converter and the PCM. If that's incorrect I'm sure someone will point it out
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Old 10-06-2008, 08:27 PM
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If I read the warranty correctly the only items covered after the 3yr/36,000 are the catalytic converter and the PCM. If that's incorrect I'm sure someone will point it out
Well, I took the Magnum to the hangar today and brought home the Commander so I actually can get to the O/M and read through.
Wow!
Talk about vague!
Anyways, after reading through my 2007 Warranty info booklet I'm left with a resounding.....maybe.
Here's why: First, on my page 18 section 5.1, I see what you read where the fed warranty only requires 2/24 coverage and mopar has graciously added 1 year and 12 k miles to that, so, we agree.
However, on page 20 section 5.2 it refers to the federal emission warranty that is for 8/80k miles.
I quote" The Emission Performance Warranty covers the cost of repairing or adjusting ANY (caps mine) component or parts that might be needed for your vehicle to pass Federal Emission Standards for a federally approved state or local emission test, but only if......"
Well there's the rub, sort of.
Since this is a OBDII system it is self testing. For those who don't know OBD is Onboard Diagnostics version 2.
Anyways, your vehicle performed a self test and it failed, hence, the light.
If you are in a county that has emission tests (I do) they cannot/will not perform a test on a car with a ck/eng light on. It is a automatic failure.
So, the catch 22 is they (Jeep) want proof of failure before the emission performance warranty kicks in. A real paradox.
However, the real proof of failure is the illuminated ck/eng light.
Trouble is, this can make warrantee coverage a bit discretionary on the dealers part.
A lawer would be proud.
So, call your dealer. I believe, following the guidlines of the feds, the O2's would be covered.
If he doesn't agree, I'd call a second dealer and so on.
I can call my dealer in Illinois (49 state emissions) if you wish.
His answer will be the definitive one if you feel like you are getting vague answers.

Gosh, I hope I didn't muddy the water too badly on this one,

........Rob
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Old 10-06-2008, 08:37 PM Thread Starter
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So are you saying that the Fed warranty only kicks in if you live in a emissions regulated area or does the whole US fall under the Feds regulations?

I live near the Quad Cities and there are no emissions test counties nearby.

I cleared the light by disconnecting the battery. We'll see if it returns. Maybe some bad gas?
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Old 10-06-2008, 08:47 PM
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Quote:
Originally Posted by jcoulter View Post
So are you saying that the Fed warranty only kicks in if you live in a emissions regulated area or does the whole US fall under the Feds regulations?

I live near the Quad Cities and there are no emissions test counties nearby.

I cleared the light by disconnecting the battery. We'll see if it returns. Maybe some bad gas?
You would be covered under the federal regulations.
Clearing the code is the first step in good diagnostics, as it is not uncommon to have a piece of carbon hang on a O2 sensor at times.
Then, through use it gets blown in the clear and the sensor returns to normal.
Sometimes, even a false code occurs and has nothing to do with the component in question.
So, if the light stays off, in this case your probably fine since the 02 is sampling at all times when the computer is in closed loop.
Then you can write it off as nothing more than an anomoly

.............Rob
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Old 10-06-2008, 08:50 PM
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Oh yeah, your first question,

California gets its very own warrantee.
So, there's California standards and there's Federal (49 state) standards.

........Rob
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Old 10-06-2008, 08:58 PM Thread Starter
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Clearing the code is the first step in good diagnostics,
.............Rob
I only cleared it so that the light wouldn't annoy me.

Thanks so much. You have been a great help.
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Old 04-05-2009, 01:40 PM
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My XK just popped the P0420 DTC code yesterday after a trip to Spokane from Missoula (~200 miles). Because it was the 420 code, I figured maybe it just needed to get high. After reading here I see its an emissions issue. The Jeep seemed to run fine on the way home, so I wasn't worried. I just disconnected the battery for about a minute to reset the codes and see if it comes back. If it does, I'll take it in - if not, I'll call it a fluke.

Glad to be able to use the forum to figure out what was going on.

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Old 04-05-2009, 02:02 PM
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P0420 OBD-II Trouble Code

Technical Description
Catalyst System Efficiency Below Threshold (Bank 1)

What does that mean?
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor
reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.


You will likely not notice any drivability problems, although there may be symptoms.

Causes
A code P0420 may mean that one or more of the following has happened:

•Leaded fuel was used where unleaded was called for
•An oxygen sensor is not reading (functioning) properly
•The engine coolant
temperature sensor is not working properly
•Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
•Retarded spark timing
•The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible Solutions
Some suggested steps for troubleshooting a P0420 code include:

•Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
•Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
•Inspect the downstream heated oxygen sensor (HO2), replace if necessary
•Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

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Last edited by jeep5253; 04-05-2009 at 05:17 PM.
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