Results 1 to 4 of 4

Thread: P0420 Code Question

  1. #1
    Been Around the Block monstrousmac's Avatar
    Join Date
    Jan 2013
    Location
    Tucson AZ
    Posts
    495

    P0420 Code Question

    Ok, so here is the scenario. I originally got a check engine light about a month ago, i turned the key three times and it spit out the P0420 code. So, I knew I had a cracked driver side exhaust manifold for a few weeks. I waited about three weeks to change it. It was in the negative teens in Montana. I changed the exhaust manifold, reset the engine code with my AEV Procal. I drove to Tucson AZ, the code came back. I changed the upstream and downstream 02 sensor. Before I did this the code would come back within a mile of driving.

    After I changed the O2 sensor the code would stay off for a couple of days. Also, when the check engine light comes on and I cycle the key three times the diagnostics just says “done” no code. When I hook up an actual scanner it does say P0420. I could drive on the interstate no code doing 70 mph. When I come off the highway at about 30 mph it came back on. It seems to be longer and longer before the code comes back. I took it to a reputable exhaust shop to replace the catalytic converter, the owner did some checks and found some bolts loose by the manifolds. He said I should not change the catalytic converter, and too reset the code a few times to allow the vehicle to go through a few driving cycles. He said the pressure coming out of the tail pipe is fine and it is not clogged.

    So, does anyone have any ideas? Does it sound right to reset it 4 or 5 times and allow the vehicle to go through a couple of driving cycles. The motor does not run rough and idles fine.

    Forgot, it is a 2010, 3.8 liter with 171,489 miles. I changed the spark plugs a few months ago, with live wire and a screaming demon coil pack.
    Last edited by monstrousmac; 02-12-2019 at 12:53 AM.

  2. #2
    Meme King WJCO's Avatar
    Join Date
    Sep 2015
    Location
    Colorado
    Posts
    25,755
    If it's not completely plugged, it still could have enough of a restriction for the o2 monitor to trigger a code. Might want to run a couple of higher octane fuel tanks or some BG 44k to see if you can clean any carbon out. No guarantee but worth a try.
    Jeep parts and accessories purchased through the following link will help support this forum and at no cost to you.
    RECOMMENDED JEEP PARTS & ACCESSORIES



    Support the JL forum: JLWRANGLER.COM

  3. #3
    Fresh Catch
    Join Date
    Jul 2016
    Location
    Fletcher NC
    Posts
    23
    You need to read the data stream. If the PCM sees the downstream oxygen sensor reading flunctuating, it senses the cat is no longer efficient. An efficient cat would make the outgoing exhaust generate a very steady oxygen sensor signal. The upstream sensor will bounce rich/lean, rich/lean but the downstream should be steady.

    If you see the DS sensor signal flunctuating much at all and there are no leaks between the 2 sensors on that bank, you have a bad cat.
    99 Ranger Truggy
    5.0, Atlas, 40" Treps

  4. #4
    Been Around the Block monstrousmac's Avatar
    Join Date
    Jan 2013
    Location
    Tucson AZ
    Posts
    495

    Update

    Well checked the downstream O2 sensor and it was fluctuating from .155 to .760, the other Downstream O2 sensor was steady at .760. My fuel trim was also high. So, I had the Catalytic converter changed for 300 dollars and every thing seems fine. No, codes or check engine lights for right now.

Similar Threads

  1. P0420 bank 1
    By 74CJ5 in forum Jeep JK Wrangler
    Replies: 6
    Last Post: 08-09-2018, 02:10 PM
  2. When it rains it pours. ODB P0420.
    By Omnifox in forum Jeep JK Wrangler
    Replies: 2
    Last Post: 03-07-2018, 04:37 PM
  3. P0420 code
    By Trigg in forum Jeep JK Wrangler
    Replies: 14
    Last Post: 04-15-2016, 03:07 AM
  4. Code P0585
    By hunterbilt in forum Jeep JK Wrangler
    Replies: 0
    Last Post: 01-25-2015, 06:34 PM
  5. Replies: 3
    Last Post: 10-19-2014, 05:28 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
“wayoflife” is a moniker that I’ve been using for 20 years now and I chose it because I think it does a great job of explaining, in simple terms, the passion I have for Jeeps and the Jeep way of life. This is a lifestyle that transcends age, gender and race as the only thing you need to be a part of it is a love for the outdoors, a desire to explore, a yearning to take on a challenge and a will to conquer it. Over the years, Cindy and I have attempted to capture the essence of this lifestyle through photographs and videos and share it with others around the world. And, this is how WAYALIFE was born.
Join us
WATCH OUR VIDEOS