Codes P0420 & P0430

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

h2100

Member
Joined
May 26, 2010
Posts
81
Reaction score
8
Location
White Lake, MI
Hello All,

My 2010 Tahoe with 185,000 miles has posted these codes. Before I jump in and replace the rear, single, catalytic converter, does anyone have a different plan? I see they can be bought for $150-$250. Any brand preferences? MagnaFlow?

I wish to sell the car soon so I wish for a proper repair with no 'check engine' light.

I await your wisdom!
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,431
Reaction score
32,206
Location
Willamette Valley
I would lean toward the oxygen sensors unless you have the cat tested for back pressure problems and find some. Rule of thumb says to replace all sensors when you do them and leave the cat(s) alone if they are ok. If the cat(s) need replaced, then do the sensors at the same time. Your codes are pointing at the sensors not liking cat efficiency, bank 1 and bank 2.
 
OP
OP
H

h2100

Member
Joined
May 26, 2010
Posts
81
Reaction score
8
Location
White Lake, MI
I would lean toward the oxygen sensors unless you have the cat tested for back pressure problems and find some. Rule of thumb says to replace all sensors when you do them and leave the cat(s) alone if they are ok. If the cat(s) need replaced, then do the sensors at the same time. Your codes are pointing at the sensors not liking cat efficiency, bank 1 and bank 2.

The back pressure test, where can this be done? Replace all sensors? I think there are 4?
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,431
Reaction score
32,206
Location
Willamette Valley
As you can see by the pic you have 2 catalytic convertors in that "Y" pipe. You have 2 sensors before the cats and 2 sensors after the cats. How up to date are your plugs, plug wires and last time the throttle plate/bore and MAF were cleaned and age of air filter?
 
OP
OP
H

h2100

Member
Joined
May 26, 2010
Posts
81
Reaction score
8
Location
White Lake, MI
As you can see by the pic you have 2 catalytic convertors in that "Y" pipe. You have 2 sensors before the cats and 2 sensors after the cats. How up to date are your plugs, plug wires and last time the throttle plate/bore and MAF were cleaned and age of air filter?

Yes, I see there are two little ones up front. I did a pretty good 'tube up' with these items at 150,000. Car runs very well.

Two sensors before and after the front set and the rear? So, that is 6 total?

Your info is helpful. My repair quote from the dealer was $3300. I'm feeling the $150 rear converter change will not solve my issue.
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,431
Reaction score
32,206
Location
Willamette Valley
I guess I need to rethink the cats count. I see in the description of the Walker pipe I sent you the link to that the third section is also labeled as a catalytic converter but has no sensors directly in front of and behind it.
 
OP
OP
H

h2100

Member
Joined
May 26, 2010
Posts
81
Reaction score
8
Location
White Lake, MI
I guess I need to rethink the cats count. I see in the description of the Walker pipe I sent you the link to that the third section is also labeled as a catalytic converter but has no sensors directly in front of and behind it.


I've made an appointment for the back pressure. It will be tomorrow. I'll advise on how it went.
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,431
Reaction score
32,206
Location
Willamette Valley
While they are in there, get them to also give you and document the cats inlet temps and outlet temps. Any good tech will have an infrared thermometer to easily do this with. It would add maybe 1-2 minutes of time to the diagnosis and that includes writing down/documenting the readings. Whatever they do you want all findings documented. Again, a good/honest tech will do that.
 

Forum statistics

Threads
129,711
Posts
1,820,155
Members
93,018
Latest member
Mack1
Top