P0420-After Complete Exhaust Replacement - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

Closed Thread
 
LinkBack Thread Tools Display Modes
post #1 of 14 (permalink) Old 10-31-2012, 08:16 AM Thread Starter
Newcomer
 
Join Date: Oct 2012
Posts: 6
Garage
P0420-After Complete Exhaust Replacement

A few months ago, my car threw the TC P0420. I didn't have the money to deal with it then, but over the last 6 weeks, I've been trying everything I can to no avail.

First, I took it to the shop. They charged me 400 for an upstream sensor. CEL came back on. Then, they said I had to replace the cat. So I buy one off Ebay (premium based on manufacturers specs) and that didn't work. Code came back. So finally, I figure there is only one possible problem left. The downstream O2 sensor. So I buy one and replace. CEL came back! At this point, I'm confounded so I research some more, and try the spark plug savor MOD. Essentially, it pulls the sensor out of the stream. Runs rough until computer calibrates, then it starts running REAL bad. Not shifting correctly, at the right RPM's, and trans makes dropping noise when I shift to D or R. So I climb back under there and pull the MOD off. I had unplugged the battery while removing that MOD, but not 10 minutes into test drive, the CEL came back on. I figure the computer needs to relearn the operation protocols.

The engine runs a little better after removing MOD, but trans is still kinda slamming into 2nd, and a tiny bit in 3rd and 4th. I plugged the monitor in this morning and it gave me 10 different, exhaust/vacuum related codes. I figured it is still figuring stuff out so I reset it, and test drove it again. 15 minute test drive and no problems except for the slight gear slippage into 2nd. I turned the car off and when I turned it back on, CEL reposted. Typically, it takes a week for the CEL to throw the P0420, but now, my CEL hit fast.

What am I gonna do about this thing? I bought the parts, and did all the work myself cause I'm broke. When I do take it to the garage, They are gonna create a huge list of vacuum leaks, and god knows whats else to try to charge me for. Any insite, or reassurances would be totally appreciated.
jbusby47 is offline  
Sponsored Links
Advertisement
 
post #2 of 14 (permalink) Old 10-31-2012, 08:47 AM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
Maybe you didn't know this, so I'll post it for you because a new cat can set the 420 code for the first 100 miles or so.

DTC Descriptor
DTC P0420: Catalyst System Low Efficiency


Circuit/System Description
Important: A new converter with less than 100 miles on it may set DTC P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

A 3-way catalytic converter (TWC) controls emissions by converting hydrocarbons (HC) and carbon monoxide (CO) into carbon dioxide (CO2), and oxides of nitrogen (NOx) into nitrogen. The TWC also stores oxygen. When the listed driving conditions are met, the Catalyst System Efficiency test will run. The powertrain control module (PCM) monitors this oxygen storage capacity by comparing the pre and post-catalyst oxygen sensor signals while adding and subtracting fuel during specific driving conditions. The PCM compares the pre and post-catalyst oxygen sensor signals to determine if the oxygen storage capacity of the catalyst is degraded.

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #3 of 14 (permalink) Old 10-31-2012, 10:00 AM Thread Starter
Newcomer
 
Join Date: Oct 2012
Posts: 6
Garage
Thanks for the response.

Yeah, I was aware of that and gave it almost 400 miles after cat replacement.
jbusby47 is offline  
 
post #4 of 14 (permalink) Old 10-31-2012, 10:39 AM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
It might be the ground connection of the HO2 circuit then.

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #5 of 14 (permalink) Old 11-01-2012, 10:25 AM Thread Starter
Newcomer
 
Join Date: Oct 2012
Posts: 6
Garage
Any idea how I would go about teching that?
jbusby47 is offline  
post #6 of 14 (permalink) Old 11-02-2012, 10:37 AM
Forum God


 
BboyTaktix's Avatar
 
Join Date: Oct 2009
Location: CANADA! Montreal (party city), Quebec
Posts: 3,229
Quote:
Originally Posted by jbusby47 View Post
Any idea how I would go about teching that?
Check the ground. Make sure it is properly grounded.

BboyTaktix
- 2011 Plasma Blue pearl WRX STI sedan
- SOLD -S256 TURBO 2.2 -SS/TC body, SS/Tc shocks/struts, B&G springs, 17"mags, TRS FX-R retrofits (50W/6000k)
BboyTaktix is offline  
post #7 of 14 (permalink) Old 11-02-2012, 10:41 AM Thread Starter
Newcomer
 
Join Date: Oct 2012
Posts: 6
Garage
Where does the ground terminate for that sensor? The battery?
jbusby47 is offline  
post #8 of 14 (permalink) Old 11-02-2012, 10:50 AM
Forum God


 
BboyTaktix's Avatar
 
Join Date: Oct 2009
Location: CANADA! Montreal (party city), Quebec
Posts: 3,229
Check the "EXH" fuse under the hood in the engine compartment fuse box. This is the fuse for that circuit. I remember mine blew after my build and it was causing all sorts of issues. It is connected to the evap solenoid as well as the upstream (pre-cat) O2 sensor and one or two other things. Make sure the O2 sensor is properly plugged. I still get codes from my upstream O2 sensor after my build but for me it's nothing major and I know what it is more or less.

BboyTaktix
- 2011 Plasma Blue pearl WRX STI sedan
- SOLD -S256 TURBO 2.2 -SS/TC body, SS/Tc shocks/struts, B&G springs, 17"mags, TRS FX-R retrofits (50W/6000k)
BboyTaktix is offline  
post #9 of 14 (permalink) Old 11-02-2012, 04:21 PM
Super Moderator
YourCobalt.com Premium Member


 
Coby7's Avatar
 
Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Posts: 11,820
Garage
The HO2s find there grounds through the "PCM" or "ECM" depending on the year of your Car. So lots of stuff would be screwed up if it was this ground. But like BBoy says check the fuses or the connector at the "PCM" or "ECM".

Every minute spent angry is a happy minute lost for ever and ever!!!
Drives 2016 Cocoa Buick Encore 1.4L Turbo auto KL4CJDSB2GB652675
Drives 2016 Sunset Orange Trax LT1 1.4L Turbo auto 3GNCJPSB8GL142716

Never drive faster than your guardian angel can fly
Coby7 is offline  
post #10 of 14 (permalink) Old 11-02-2012, 04:52 PM
Expert


 
blu3_v1p3r's Avatar
 
Join Date: Mar 2010
Location: Ventura County, CA.
Posts: 922
what brand o2 sensor did you get. There have been a ton of problem with the Bosch o2 sensors. Best way to go is OEM. 400 for a dealer to do an o2 sensor is robbery. The o2 sensor cost 50+/- a few and it takes 15 mins to change it. 1 hr maint at say 80 per hour. At the absolute most is should have costed through the dealer or any shop is 200, and thats on the extreme high side

2009 Imperial Blue Metallic Cobalt SS/TC Sedan - "Stock":
2008 Victory Red HHR SS - Stock
2005 Chili Pepper Red Ion Redline - Stock
2007 Sunburst Orange Metallic LS Coupe - Sold
blu3_v1p3r is offline  
Sponsored Links
Advertisement
 
Closed Thread

Tags
2006 , cobalt , low cat threashold , o2 sensor , p0420

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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 On
Pingbacks are On
Refbacks are On

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