Hey all, just looking for a little help with my moms truck.

Its a 2004 Silverado with 71k and it just recently started having a few problems. Of course she didn't bring it to my attention until she was leaving tonight, but her her engine light has been on for about a week. I pulled a code 0420 with my little launch obdII reader and I am getting some mixed signals. I am thinking it is the O2 sensor, but when I search the forums I get a possible catalytic converter. I've searched here but don't seem to get any info. on a code 0420.
I race a 92 Mazda Miata so I dont have a lot of experience with Chevy.
I was going to have her come back by tomorrow so I could swap the O2 out....is there anything else I should look for? On some trucks there is a precat and after cat 02, but I only see one on hers.

What about the catalytic converter? Is it under a seperate warranty? A bad cat at 71k doesnt sound right for a truck being driven by a grandma. I've read that the cat is warrateed up to 80k, but that is just a poster in another forum mentioning that, not a GM rep.

Any help is appreciated.

 

P0420 = catalyst sytem efficiency below threshold bank 1 ... check for leaks before the cat.

Check the owner's manual about what's covered under the emissions warranty and for how long.

 

Basically this means that the oxygen sensor downstream (after) your Chevy catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system. You will likely not notice any drivability problems, although there may be symptoms... Some causes of this code are leaded fuel was used where unleaded was called for, an oxygen sensor is not reading (functioning) properly, the engine coolant temperature sensor is not working properly, there is a damaged exhaust manifold / catalytic converter / exhaust pipe or a retarded spark timing... Either way, the simplest thing to do is to reset the code and see if it comes back. Next step is to measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). The voltage should be low and steady (~200mV, depends on the vehicle). If the voltage varies (e.g. 100mV to 600mV) then it's time to replace the catalytic converter. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it. One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into. Good luck!!!