Hello and HELP! CODE P0420 - DodgeForum.com

3rd Gen Ram Tech 2002-2008 Rams: This section is for TECHNICAL discussions only, that involve the 2002 through 2008 Rams Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.

Hello and HELP! CODE P0420

Thread Tools Search this Thread
Old 12-09-2007, 11:39 AM
DonnasDodge DonnasDodge is offline
Thread Starter
Join Date: Dec 2007
Posts: 3
Default Hello and HELP! CODE P0420

Hello everyone and this is my first post on the forum. I love my truck although I haven't done a ton to it, just but 35" tires. Just wanted to say hey and I plan on being part of this family for awhile since I still have a lot of plans for the truck.

Anyway, sorry to jump in with a problem, but I have one. After a 800 mile trip to and from Reno, our truck threw a CEL. The code is P0420. I had this checked recently and it came up with the following:

Catalyst efficiency low-bank 1

The oxygen sensors monitor the catalytic converters ability to store oxygen.

Probable Causes
1.) Catalytic Converter defective (Failure possibly due to #2, 3, or 4)
2.) Engine misfire or running condition
3.) Large Vacuum leak
4.) Engine oil leakage into exhaust-valve guide seals, piston rings

Now some backstory. Right now with Christmas coming, I don't want to take it down to someone right yet with out trying to figure this out a little by myself. I have had people recommend replacing the O2 sensors, but after checking it looks as if there are 4 of them (2 before and 2 after the CC).

What would you guys recommend? I really would like to get this solved without having to shell out tons of cash right before the Holidays.

Thanks again for everyone's help.

Reply With Quote
Old 12-09-2007, 05:14 PM
DonnasDodge DonnasDodge is offline
Thread Starter
Join Date: Dec 2007
Posts: 3
Default RE: Hello and HELP! CODE P0420

Reply With Quote
Old 12-09-2007, 05:42 PM
CarGuyOhio's Avatar
CarGuyOhio CarGuyOhio is offline
Admin formally known as 94rt10ohio
Join Date: Apr 2005
Vehicle: 12 Challenger SRT Yellow Jacket, 14 Wranger Sahara 2 Door
Location: Curtice, OH
Posts: 9,017
Default RE: Hello and HELP! CODE P0420

#2 should be out. There are codes that would show up for misfires

#3 should be easy to hear

#1 would require to to put oil in the truck often

May also help to state year, miles, engine, ect.
Reply With Quote
Old 12-09-2007, 05:48 PM
Gone Fishin Gone Fishin is offline
Record Breaker
Join Date: Feb 2005
Vehicle: 2005 5.7,2500,G-56 6spd, 4x4,SB---2005 3500 Dually, 5.9, 4x4, NV5600 6spd, LB
Location: Bristol, IN
Posts: 2,287
Default RE: Hello and HELP! CODE P0420


It would really help if we knew what exactly you are running. I'm assuming a 5.7L Hemi, In which case I would start out by checking for a vacuum leak, especially around the charchol canister and associated lines. It should be located under the truck in the frame rails behind the driver. The hoses are just plain old rubber, and if they crack much, you get a large air leak. Next, If you're not seeing blue smoke on startup, chances are the valve seals are ok. I would wait until you check out the vacuum possibility before I would spring for the O2 sensors (after the converters). How many miles, last tune-up??? etc.
Reply With Quote
Old 12-22-2007, 12:06 PM
DonnasDodge DonnasDodge is offline
Thread Starter
Join Date: Dec 2007
Posts: 3
Default RE: Hello and HELP! CODE P0420

There are about 57k on the truck and its a 2005 Dodge Ram 1500 QDCB Hemi. Last tune up was about 900 miles ago, but will be needing to do the 60-75k service soon.

Which hoses should I check first? Is there a way of determining that it is a vacuum leak other than visual inspection?

Thanks again everyone for your help. Trying to avoid a fat charge from a mechanic to just figure out the problem, then another fat charge for the solution.

Merry Christmas!
Reply With Quote
Old 01-12-2008, 08:07 AM
Rabies Rabies is offline
Join Date: Dec 2004
Posts: 5
Default RE: Hello and HELP! CODE P0420

Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
Rock Auto Discount, use it or loose it Gone Fishin 3rd Gen Ram Tech 1 07-05-2016 07:49 PM
[4th Gen : 01-07]: Rough Idle/O2 Sensor Issues...HELP!!! Miketech137 Dodge Caravan 5 10-20-2015 07:27 PM
engine light P2433 just1creation Dodge Stratus 1 08-04-2015 11:05 AM
ODB1 Code Flashes Twice? 1995 Dodge Ram 1500 5.9L 360Ci 4x4 JoshuaYsassi 2nd Gen Ram Tech 21 07-28-2015 11:16 AM
Getting the P0601 code on our 2001 Dodge Stratus SE Sedan Stratus0159 Dodge Stratus 2 07-16-2015 11:22 PM

06, 1500, 2005, 57, bank, blue, caravan, charger, code, dakota, dodge, hemi, location, p0420, ram, rt, smoke, start

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

All times are GMT -4. The time now is 06:29 AM.