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#4621560 - 01/02/18 10:09 AM 2006 chrysler 3.5 300
jeep58 Offline

Registered: 02/06/09
Posts: 40
Loc: ny
Hi I have this car with 75k on it got it from original owner, the code P0420 came on I reset it with scan tool. it will come on again the car uses oil in between oil 3.5 engines are know for that. The car has plenty of power so cats are not completely clogged. Why would the cat be going so soon and has anyone with this engine 3.5 had the same problems?

#4621585 - 01/02/18 10:34 AM Re: 2006 chrysler 3.5 300 [Re: jeep58]
Rolla07 Offline

Registered: 11/05/11
Posts: 4563

Check for holes in exhaust pipe, 02 sensor etc.
2007 Corolla Red Pearl 151k miles
Castrol Magnatec 0w20 & Napa Proselect

#4621777 - 01/02/18 01:29 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
jeep58 Offline

Registered: 02/06/09
Posts: 40
Loc: ny
I have a friend that owns a garage the system is all stainless steel no leaks, I know theses engines use oil just wandering if that is the cause of the check engine light coming on!

#4621911 - 01/02/18 03:50 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
JMJNet Offline

Registered: 09/06/07
Posts: 883
Loc: TX, USA
P0420 is usually O2 sensors, there are usually sensors before and after the cat.
Depending on the engine there may be 2 before and 2 after.
At least that was my experience with the Toyota.

You may need to check the forum specific for your car manufacturer to check with their experience fixing this code.

BITOG is more of a generic forum for this type of issue.

Edited by JMJNet (01/02/18 03:53 PM)
  • 2017 Toyota Sienna
  • 1995 GMC Suburban 6.5L Turbo Diesel

#4621941 - 01/02/18 04:20 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
ejes Offline

Registered: 01/11/16
Posts: 303
Loc: Kansas
As said previously, likely an O2 sensor. Some say to replace them all at once if you can, some say just replace them as they go bad. If I can find them all fairly cheaply, and its on a car/truck with a lot of miles or age, I do them all when one fails. I've had good luck with Denso and NTK. I believe the 06 300 V-6 gas 2 upstreams and 2 downstreams and they are all the same model of sensor. You can get NTK's for 25 bucks at RA.

#4621942 - 01/02/18 04:23 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
jeep58 Offline

Registered: 02/06/09
Posts: 40
Loc: ny
Ok Thanks there are 2 sensors on the cat one before and one after any idea as to which one could be bad?

#4621959 - 01/02/18 04:44 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
ejes Offline

Registered: 01/11/16
Posts: 303
Loc: Kansas
Inspect them first for loose or broken wires, etc. I generally suspect the downstream first, but the only way to really tell is with a scan tool that tells you. Some do and some don't. Sometimes AZ and other auto parts places will scan it and tell you if you buy the part there. There are ways to test them with voltmeters, etc. if you google it.

#4622008 - 01/02/18 05:28 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
thorromig Offline

Registered: 03/22/12
Posts: 804
Loc: BerksCounty/Pa.
My good friend a head mechanic at a Cadillac dealership says "always" use OEM O2 sensors when replacing them.
00 Dodge Ram 5.2L 4x4 Edge 10W30 FU (91K)
08 Acura TL Type S 3.5L PUPP 5W20 FU (101K)
17 Jetta TSI SE 1.4L Turbo - Edge 0W40 FU (Hers) (4K)

#4622012 - 01/02/18 05:35 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
HoosierJeeper Offline

Registered: 11/23/16
Posts: 1221
Loc: WI
Only use NTK on anything Mopar! O'Reillys carries them.
15 Jeep KL Limited V6: Formula Shell 5W20
07 LR3 SE V8: Maxlife 5W30
05 Jeep KJ Limited: PHM 5W30
96 Jeep XJ Country: STP HM 5W30 (winter)

#4622051 - 01/02/18 06:18 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
clinebarger Offline

Registered: 12/19/13
Posts: 1636
Loc: Fort Worth, Texas
Swap the O2 sensors left to right, If you now get a P0430....It's the O2 sensors.

I would bet money it's NOT the O2's
2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2007 Chevy Cobalt SS LSJ/F35
2010 Toyota Corolla 2ZR-FE/Auto

#4622064 - 01/02/18 06:30 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
jeep58 Offline

Registered: 02/06/09
Posts: 40
Loc: ny

#4622075 - 01/02/18 06:37 PM Re: 2006 chrysler 3.5 300 [Re: HoosierJeeper]
jeepman3071 Offline

Registered: 04/15/10
Posts: 4042
Loc: Storrs, Connecticut
Originally Posted By: HoosierJeeper
Only use NTK on anything Mopar! O'Reillys carries them.

Yup. Lots of guys on the Jeepforums who use Bosch or something else and have issues or poor fuel economy.
2000 Jeep Cherokee Sport 4.0L (178k) - Pennzoil HM 5w30, Napa Gold 1516, Magnefine trans filter

#4622147 - 01/02/18 07:50 PM Re: 2006 chrysler 3.5 300 [Re: jeep58]
Leo99 Offline

Registered: 03/30/14
Posts: 2783
Loc: NJ
From what I've read, worry about the ones upstream first. They are usually the ones that go bad and are usually easier to replace. I know the downstream one on my Corolla was a real bear to get out.

Changing the O2 sensors did fix the P0429 code in my Corolla.
Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles
2004 Rav4 333,000 miles
2015 Camry 40,000 miles