View Full Version : P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

11-14-2011, 01:50 PM
Just popped 2 of these codes on my 2004 Suburban w/ 137,000 on it.

Car seems to run fine, in fact just did a 1000 mile round trip from up North a weekend ago.

Suggestions on this one? O2 sensors? Cats?

Formula WS6
11-14-2011, 01:56 PM
most likely a converter replacement is needed. You can go aftermarket but they won't have near the life of an O.E. one. GM's not price that bad concidering what some cost to replace $482. There is most likely a core charge involved too untill you return the old ones.

11-14-2011, 02:39 PM
So a GM replacement would be $482? Getting damn tired of dumping cash into this turd box.

Formula WS6
11-14-2011, 05:48 PM
what is the 8th digit of your vin so I can confirm

11-15-2011, 11:11 AM
I'll check tonight. Cleared the code yesterday at lunch, drove it home last night and back to work this morning without issue. (~45 miles round trip)

Formula WS6
11-15-2011, 11:31 AM
It's in the beginning stages for sure. This time it may take a couple weeks to a month for it to pop back on. You can clear it and it will start popping on sooner and sooner.

Pro Stock John
11-16-2011, 09:54 PM
Is that one side or the other side? Maybe find a take-off?

11-16-2011, 11:36 PM
Is that one side or the other side?
If one is close or going the other is likely close behind. Short of being ran for a while with a running issue.

Maybe find a take-off?
Not legal anymore/cannot find them anymore.

11-17-2011, 11:31 AM
So you can't replace them with like a Flowmaster cat or some BS like that?

I swear I'm going to firebomb this turd and push it off a cliff.

But somehow, it is still my favorite hunting vehicle of all time. FML

Formula WS6
11-17-2011, 01:48 PM
You can go with obd2 universals (must be vehicle specific size wise for load rating) and they'll work but they don't have near the life expectancy of an OE.

11-17-2011, 02:54 PM
What kind of cost savings would that be? I need another year out of this sucker then she's gone!!