P0420 Bank 1 issue. ***Fixed! Lessons learned post added*** - Saturn Outlook Online Community
LinkBack Thread Tools
post #1 of 5 (permalink) Old 11-19-2016, 04:26 PM Thread Starter
Junior Member
Join Date: Jun 2015
Posts: 25
P0420 Bank 1 issue. ***Fixed! Lessons learned post added***

Hey all, my '09 Outlook has been running with a P0420 code for quite awhile. Even after I clear it, it returns in pretty short order. It has also been feeling like it lacks some power, and I sometimes get a burning oil type smell, especially when going up hills. My scan tool says "Bank 1", but does not specify any particular sensor.

I have had to replace 4, maybe 5, coil packs over the last couple years.

Based on online articles, I did other diagnostics, and everything I could check with the tool seemed to be ok, so I figured a cat had her ne bad, maybe due to the faulty coil packs.

Most everything I have read online said "Bank 1" is the firewall side, so I finally tore into it today, pulling that cat off. Looking at it, there is no obvious damage to the honeycomb. That said, whereas I was able to easily see light through the rearmost cat (the one right in front of the muffler), I can only see light through the firewall one by taking it into a dark room and shining a flashlight through it.

I came inside to do a little more research, and found a couple places saying bank 1 is the radiator side, so many w I really have no idea which is right. I won't be able to pull the radiator side cat off until I buy an O2 sensor socket, but I'm thinking Inshould go ahead and pull it off to check its condition, in case that is actually bank 1.

Also, the downstream side O2 sensor for the radiator side cat has a lot more carbon type buildup on it than the downstream side sensor for the firewall cat.

Can anyone tell me, definitively, which side is "bank 1"? And whether I should be able to see light easier through the cat? Any other ideas?

SR is offline  
Sponsored Links
post #2 of 5 (permalink) Old 11-21-2016, 04:44 PM
Senior Member
Join Date: Oct 2009
Posts: 754
Re: P0420 Bank 1 issue.

Bank 2, sensor 1..

is the O2 sensor on top- front of engine-- that is the one very close to the oil dipsticks.


2010 FWD LT1-Gold Mist Metallic- seats 8.<br />Build Date- July 31, 2009-2nd day of Spring Hill 2010 production.<br />2013 Equinox 3.6L -&nbsp; &nbsp; 16,755<br />2010 Traverse 3.6L-&nbsp; &nbsp; 74,300<br />2003 Trailblazer 4.2L-170,500
rbarrios is offline  
post #3 of 5 (permalink) Old 11-21-2016, 11:18 PM Thread Starter
Junior Member
Join Date: Jun 2015
Posts: 25
Re: P0420 Bank 1 issue.

Originally Posted by rbarrios
Bank 2, sensor 1..

is the O2 sensor on top- front of engine-- that is the one very close to the oil dipsticks.

Terrific, thank you. I talked to a guy at NAPA, he said the bank 1 usually corresponds to the side with the #1 cylinder, but your post certainly confirms what I expected. I presume, based on your answer, sensor 1 on bank 1 would also be the one upstream of the convertor?

I've got a new bank 1 convertor coming, hopefully it'll fix the issue.
SR is offline  
Sponsored Links
post #4 of 5 (permalink) Old 11-27-2016, 01:43 AM Thread Starter
Junior Member
Join Date: Jun 2015
Posts: 25
***Fixed. Lessons learned***

Got the cat in, seems to have fixed the problem

This took me about 3.5 hours to get everything removed, 1.5-2 hours to get it all back together.

I found having a stubby, flex head ratched, as well as a regular flex head ratchet, indespensible for getting into the tight space between the firewall/floor and cat flange. Also, WD40 and a 1/2" ratchet with extensio ns and a u-joint, for breaking the nuts loose, then switching over to to the smaller ratchets so you can get a more complete swing.

It would be a good idea to some M8-1.25 and M10-1.5 exhaust studs, flange bolts, and flange nuts on hand, in case you break one off.

In addition to the above listed ratches, 13 and 15mm regular and deep sockets, 13 and 15mm Gearwrenches/end wrenches, and a 3/8" Gear/endwrench is pretty much it.

The driveshaft does NOT need to come out, but there are 2 aluminum heat shields, one between the driveshaft and frame cross member, and one between the crossmember and the cat, that need to come out to give you room to work. This is what the 3/8" wrench is for. The shild above the shaft is plenty easy to get off, but the one immediately below the cat is a little trickier because one of the screws goes right into the crossmember right below the cat. Getting it out isn't too bad, but getting it back in without dropping it is tricky. Take your time, put the other screw for this shield in place first to help keep the trickier on in alignment.

The cat flanges that mate up to the exhaust pipe have studs that are press fit, like wheel studs. I checked five different places, including a dealership, no luck finding them. A place like Fastenal might have them, but they were closed. The M10 flanged bolts worked fine.

Since I had everything apart, I went ahead and changed all the exhaust gaskets:header-to-cat, cat-to-exhaust, and exhaust-to-exhaust. I saw evidence of exhaust escaping past the paper type exhaust-to-exhaust gasket, so decided to just replace them all while I had it apart. Seeing what the new ones looked like, there is no doubt all the taking apart and putting together done by the dealership had taken a toll on the old ones. Good idea to order these the same time you order the cat so you don't have to pay dealer prices.

The O2 sensor is easiest unplugged/plugged from the passenger side wheel well, unless you have a lot of one hand dexterity.

All in all, not a terribly difficult job, just tedious.
SR is offline  
post #5 of 5 (permalink) Old 12-05-2016, 03:44 PM
Junior Member
Join Date: Nov 2014
Posts: 6
Re: P0420 Bank 1 issue. ***Fixed! Lessons learned post added***

Saw this as i posted my experience. Glad to know there was someone who suffered like me. Happy to have my CELs gone so i can use my auto-start for winter!!
crazyIvan is offline  

Quick Reply

Register Now

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

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


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

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 On
Pingbacks are On
Refbacks are On

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