P0420... Oh.. Boy! - JeepForum.com
 2Likes
  • 1 Post By 90grandoneer
  • 1 Post By Walt
 
LinkBack Thread Tools
post #1 of 6 Old 07-11-2019, 07:13 PM Thread Starter
4t5Gunner
Registered User
 
4t5Gunner's Avatar
2007 WK 
 
Join Date: Jul 2019
Location: Virginia Beach
Posts: 6
Garage
P0420... Oh.. Boy!

Hey all, doesn't it figure my first post would be a call for help. Need some input from those that may have dealt with this before or know something that I may be overlooking. I am a little confused now.

2007 JGC Limited 5.7 HEMI 114k miles

At about 2k rpm Bank one sensor one (Driver side up stream) cycling between .075v and .857v very rapidly while Bank one sensor two (Driver side down stream) was holding between .725v and .780v. Sounds about normal, right? Temp at the bank one Cat (Driver side) inlet was 468* and the outlet was 569*. A bit close but still ~100*. For a P0420 code I should have a wonky O2 sensor reading or no temp increase or even a decrease going through the Cat. If anything I may be running a bit rich on that side but nothing major.

I think that everything checks out on that side and repeat the test on Bank two to see what is going on there for a comparison...

Still 2k rpm Bank two sensor one (Passenger side up stream) cycling between .031v and .820v very rapidly while Bank two sensor two (Passenger side down stream) was holding between .685v and .725v. Still sounding normal, right? Temp at the bank two Cat (Passenger side) inlet 577* and the outlet 497*. Hmmm... That does not seem right, however no P0430 code.

I repeat the test at idle with the following results...

Bank one sensor one cycling between .055v and .812v. Bank one sensor two holding between .760v and .780v. Bank one Cat inlet 337* and outlet 445*

Bank two sensor one cycling between 0.072v and .793v. Bank two sensor two holding between .790v and .800v. Bank two Cat inlet 374* and outlet 399*

So... Looks like all the O2s are good but my Bank 2 Cat is going out. Nothing pointing to a P0420 code and I do not have a P0430 code. What am I missing?

Thanks i advance for any and all input!

4t5Gunner is offline  
Sponsored Links
Advertisement
 
post #2 of 6 Old 07-12-2019, 12:17 PM
90grandoneer
Moderator
 
90grandoneer's Avatar
2006 WK 
 
Join Date: Apr 2008
Location: City of Trees
Posts: 3,650
Welcome to the forum. Sounds to me like you have a pretty good handle on everything. Yes, your O2's all seem to be within the proper ranges. It appears you're using celsius temperatures....I hope. What RPM were the first tests done at and was the engine fully warmed up and operating in closed loop? Have you checked for exhaust leaks on both sides, especially at the exhaust log manifolds where they bolt to the heads? This is a very common leak point on the Hemi's (broken bolts/studs) and can cause several different fuel management codes to be thrown. What's your fuel economy been like.....city/mixes/highway, figured with a calculator? What kind of fuel are you running (top tier or off brand) and what octane? What altitude are you located at?
4t5Gunner likes this.

06 GCO, Dk Khaki, QDII, Flshing Hi 3rd Bk Lt, MDS "ON" Lt, Airtab Vortex Gens, Debadged, Fumoto Drain Valve, BT Catch Can, Chopped EGR Tube, SRT8 CAI, TruFlow Filter, Sonnax Trans Line Press Booster, SC Tuner W/Adv Trans Tune App, DS and HP tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvr, SRT8 frt/rear bumpers, FRI Sidewinder Cam w/6* advance/6.1 valvetrain, SLP 25% UD Pulley, BBK true 90mm T-Body, SOS Ign Coils w/.060 spark plug gaps, TEA ported/milled heads w/new valve seats, SRT Reps with 265/45&295/40X20's. Also 05 Hemi LX modded exactly like WK and Comp Cammed 06 300CSRT8.
90grandoneer is offline  
post #3 of 6 Old 07-12-2019, 01:16 PM
Walt
Registered User
2008 WK 
 
Join Date: Oct 2009
Location: Midland
Posts: 2,347
Quote:
Originally Posted by 4t5Gunner View Post
...2007 JGC Limited 5.7 HEMI 114k miles

At about 2k rpm Bank one sensor one (Driver side up stream) cycling between .075v and .857v very rapidly while Bank one sensor two (Driver side down stream) was holding between .725v and .780v. Sounds about normal, right? Temp at the bank one Cat (Driver side) inlet was 468* and the outlet was 569*. A bit close but still ~100*. For a P0420 code I should have a wonky O2 sensor reading or no temp increase or even a decrease going through the Cat. If anything I may be running a bit rich on that side but nothing major.

I think that everything checks out on that side and repeat the test on Bank two to see what is going on there for a comparison...

Still 2k rpm Bank two sensor one (Passenger side up stream) cycling between .031v and .820v very rapidly while Bank two sensor two (Passenger side down stream) was holding between .685v and .725v. Still sounding normal, right? Temp at the bank two Cat (Passenger side) inlet 577* and the outlet 497*. Hmmm... That does not seem right, however no P0430 code.

I repeat the test at idle with the following results...

Bank one sensor one cycling between .055v and .812v. Bank one sensor two holding between .760v and .780v. Bank one Cat inlet 337* and outlet 445*

Bank two sensor one cycling between 0.072v and .793v. Bank two sensor two holding between .790v and .800v. Bank two Cat inlet 374* and outlet 399*

So... Looks like all the O2s are good but my Bank 2 Cat is going out. Nothing pointing to a P0420 code and I do not have a P0430 code. What am I missing?
1. I agree with 90grandoneer's comments. The values and reported behaviors of your O2 sensors seem normal. If they have over 100-120K miles, they are probably becoming due for replacement soon. I'd wait until you do the other checks first.

2. A small exhaust leak will cause this DTC. Recommend you closely examine the rear end of the LHS exhaust manifold and the exhaust manifold-to-Y-pipe joint for broken or loose fasteners. I have to periodically tighten this area on my RHS components. If the joints are loose, I get P0153 (O2 sensor 2/1 slow response) and/or P0430 (Cat 2 low efficiency) DTC's, but only sporadically and unpredictably.

3. There is a smoke test that can be performed to look for leaks also. Easy to do but only if you have the right equipment (very low pressure air and a smoke generator). It pressurizes the exhaust system and injects a smoke into it. The dealer had to do it several times to find the condition described in item #2 above.

4. You can try tightening the capscrews and nuts and then re-setting the DTC's. BTW: DTC P0420 will be pending (no MIL) the first occurrence and then set (MIL illuminated) on the 2nd one.

5. If you do decide to replace the Y-pipe, get your build sheet (VIN at dealer's parts dept.) to find out if you have Federal or Calif/NY emissions. Likely a significant difference in price.

One member reported that the smoke test revealed a tiny leak in the collector area of the Y-pipe and that set off his DTC's.
4t5Gunner likes this.

HEMI CLUB MEMBER #45; SILVER WK CLUB MEMBER #13
'08 WK GC Limited. 5.7L HEMI. Quadra-Trac II. Bright Silver Metallic. Class IV hitch.
Michelin LTX M/S tires. Fumoto oil drain valve. Billet Technology oil catch can.
Walt is offline  
 
post #4 of 6 Old 07-12-2019, 08:10 PM Thread Starter
4t5Gunner
Registered User
 
4t5Gunner's Avatar
2007 WK 
 
Join Date: Jul 2019
Location: Virginia Beach
Posts: 6
Garage
Update: I erased the code last night and went for a 20 minute joy ride. It did not come back as active or pending. Drove to work this morning, still no light, Code not active however it set as pending. Drove home made a couple of stops on the way, same thing. FYI about 30-45 minute trip to and from work most of it 45mph with several stop lights with about 10 minutes of 55-65mph sustained. Took a quick look/listen for exhaust leaks, nothing definitive. Most times I have heard a leak on the HEMIs it is pretty pronounced. It does seem to have a slight "HEMI tick" from the drivers side Valve cover.

Thanks for the input guys.

Quote:
Originally Posted by 90grandoneer View Post
Welcome to the forum. Sounds to me like you have a pretty good handle on everything. Yes, your O2's all seem to be within the proper ranges. It appears you're using celsius temperatures....I hope. What RPM were the first tests done at and was the engine fully warmed up and operating in closed loop? Have you checked for exhaust leaks on both sides, especially at the exhaust log manifolds where they bolt to the heads? This is a very common leak point on the Hemi's (broken bolts/studs) and can cause several different fuel management codes to be thrown. What's your fuel economy been like.....city/mixes/highway, figured with a calculator? What kind of fuel are you running (top tier or off brand) and what octane? What altitude are you located at?
Thanks for the welcome, looks like a pretty good forum to be apart of, hopefully I will be able to contribute as I learn more about these vehicles. Pretty familiar with the LXs and LAs with HEMIs. I am looking forward to the experience. So first off all the temp readings were in Fahrenheit. I conducted the first set of tests at ~2,000 rpm. I had just driven about 30 minutes home from work then conducted the tests. I am not to sure how to verify when it is operating in Closed loop vs Open loop. As far as I know once the motor is up to temp the fuel should go into closed loop. Is there a way to verify that? As mentioned above I took a quick look/listen for leaks. I will get it up on some ramps in the morning and get a good hands on look at everything. The fuel economy has been about 13ish according to the cpu. I have not actually logged the gallons and miles yet. I do not mess with the off brand fuel stations. 87 octane BP, Shell or Sonoco are pretty much it, no 7-11, Wawa or Grocery store gas. I have thrown in a can of Seafoam with the last two tanks once they got to about 3/4. And finally I am at sea level here.

Quote:
Originally Posted by Walt View Post
1. I agree with 90grandoneer's comments. The values and reported behaviors of your O2 sensors seem normal. If they have over 100-120K miles, they are probably becoming due for replacement soon. I'd wait until you do the other checks first.

2. A small exhaust leak will cause this DTC. Recommend you closely examine the rear end of the LHS exhaust manifold and the exhaust manifold-to-Y-pipe joint for broken or loose fasteners. I have to periodically tighten this area on my RHS components. If the joints are loose, I get P0153 (O2 sensor 2/1 slow response) and/or P0430 (Cat 2 low efficiency) DTC's, but only sporadically and unpredictably.

3. There is a smoke test that can be performed to look for leaks also. Easy to do but only if you have the right equipment (very low pressure air and a smoke generator). It pressurizes the exhaust system and injects a smoke into it. The dealer had to do it several times to find the condition described in item #2 above.

4. You can try tightening the capscrews and nuts and then re-setting the DTC's. BTW: DTC P0420 will be pending (no MIL) the first occurrence and then set (MIL illuminated) on the 2nd one.

5. If you do decide to replace the Y-pipe, get your build sheet (VIN at dealer's parts dept.) to find out if you have Federal or Calif/NY emissions. Likely a significant difference in price.

One member reported that the smoke test revealed a tiny leak in the collector area of the Y-pipe and that set off his DTC's.
As mentioned above I plan on getting her up on the ramps tomorrow and get a good look at the exhaust system. Based on both of your input I will be sure to check the Manifold bolts and all flanges and bring some wrenches with me. Checked the build sheet it was sold with Cali/NY emissions... So I don't have that going for me.
Depending on how long this goes I may look into having it smoke checked... lol.

Thanks again to both of you for your input, it is appreciated!
4t5Gunner is offline  
post #5 of 6 Old 07-12-2019, 11:45 PM
2005JGC
Registered User
 
2005JGC's Avatar
2005 WK 
 
Join Date: Dec 2017
Posts: 333
Garage
There is a P0420 or P0430 dtc post around here that I posted pictures of the tiny crack I had in my commander 5.7l exhaust that gave me a check engine lamp. It is right at the joint where the left and right banks are welded together. Smoke didnt work for crap. I may have had better luck with compressed air and a spray bottle of soapy water, but I never made that happen. I never saw the crack until I pulled the y pipe out to replace it. Fixed the problem though!

2005 Jeep Grand Cherokee - Work in progress...
2005JGC is offline  
post #6 of 6 Old 07-13-2019, 10:02 AM
90grandoneer
Moderator
 
90grandoneer's Avatar
2006 WK 
 
Join Date: Apr 2008
Location: City of Trees
Posts: 3,650
Quote:
Originally Posted by 4t5Gunner View Post
Update: I erased the code last night and went for a 20 minute joy ride. It did not come back as active or pending. Drove to work this morning, still no light, Code not active however it set as pending. Drove home made a couple of stops on the way, same thing. FYI about 30-45 minute trip to and from work most of it 45mph with several stop lights with about 10 minutes of 55-65mph sustained. Took a quick look/listen for exhaust leaks, nothing definitive. Most times I have heard a leak on the HEMIs it is pretty pronounced. It does seem to have a slight "HEMI tick" from the drivers side Valve cover.

Thanks for the input guys.



Thanks for the welcome, looks like a pretty good forum to be apart of, hopefully I will be able to contribute as I learn more about these vehicles. Pretty familiar with the LXs and LAs with HEMIs. I am looking forward to the experience. So first off all the temp readings were in Fahrenheit. I conducted the first set of tests at ~2,000 rpm. I had just driven about 30 minutes home from work then conducted the tests. I am not to sure how to verify when it is operating in Closed loop vs Open loop. As far as I know once the motor is up to temp the fuel should go into closed loop. Is there a way to verify that? As mentioned above I took a quick look/listen for leaks. I will get it up on some ramps in the morning and get a good hands on look at everything. The fuel economy has been about 13ish according to the cpu. I have not actually logged the gallons and miles yet. I do not mess with the off brand fuel stations. 87 octane BP, Shell or Sonoco are pretty much it, no 7-11, Wawa or Grocery store gas. I have thrown in a can of Seafoam with the last two tanks once they got to about 3/4. And finally I am at sea level here.



As mentioned above I plan on getting her up on the ramps tomorrow and get a good look at the exhaust system. Based on both of your input I will be sure to check the Manifold bolts and all flanges and bring some wrenches with me. Checked the build sheet it was sold with Cali/NY emissions... So I don't have that going for me.
Depending on how long this goes I may look into having it smoke checked... lol.

Thanks again to both of you for your input, it is appreciated!
The LX's and the WK's engine management systems are almost exactly the same, except for some of the programming. LX's (I have both a 5.7 and a 6.1 along with the 5.7 WK) have better exhaust logs and don't seem to have the same leak problem as the WK's with the stock logs. I think the problem is the "Y" piped single exhaust as opposed to the duals on the LX Hemi's. Closed loop should be obtained in less than a minute after cold start (usually less than ~45 seconds or so), and your "fairly normal" fuel economy would indicate this is working properly. You'll need a scanner with this capability to check it. I have DashHawks (no longer made....BOO!) in all 3 of mine, and they have this capability.

Your 2000 RPM cruise catalytic converter temps. are a little lower than mine run. When you took these cruise readings, were you at extremely light throttle with almost no load, or were you under a fair load? As an example, on the highway at fairly normal cruise in 4th gear at about 2200-2300 RPM with the MDS on, mine will run around 1200*F.

Keep us posted on your findings.

06 GCO, Dk Khaki, QDII, Flshing Hi 3rd Bk Lt, MDS "ON" Lt, Airtab Vortex Gens, Debadged, Fumoto Drain Valve, BT Catch Can, Chopped EGR Tube, SRT8 CAI, TruFlow Filter, Sonnax Trans Line Press Booster, SC Tuner W/Adv Trans Tune App, DS and HP tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvr, SRT8 frt/rear bumpers, FRI Sidewinder Cam w/6* advance/6.1 valvetrain, SLP 25% UD Pulley, BBK true 90mm T-Body, SOS Ign Coils w/.060 spark plug gaps, TEA ported/milled heads w/new valve seats, SRT Reps with 265/45&295/40X20's. Also 05 Hemi LX modded exactly like WK and Comp Cammed 06 300CSRT8.
90grandoneer is offline  
Reply

Tags
catalytic coverter , hemi , p0420

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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 On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome