It needs cats, try running a bottle of cat cleaner through it and clear the light that worked for a couple of my customers to get them through emissions.

Get a laser thermometer cheap at harbor freight. Check your catilitic converters. Check the temp directly before the cats and directly after the cats. The temp should be higher behind the cats. If the temp is higher in front of the cats, they are clogged and need to be changed.

Sounds like it needs cats. Surprising it’s both sides at once but, not impossible. Have you tried changing your down stream o2 sensor?

Everyone always says it needs cats. That’s not always the case. Find someone who knows their stuff and watch some live data. That will tell you if the cats are bad.

Clearing codes doesn’t fix the problem. 40 miles is average for a computer reset, meaning it’s a valid call-out.

Spend a lil money, mate.

Emissions are useless. Move…

Does anybody diag anymore before throwing money into shit first off is the truck running fine just the codes maybe the sensors are working as they should telling you there’s another problem rich lean something as simple as an injector can cause the cats to not do there job due to over fueling too much unburned gas can cause that code start simple without tossing parts at it test voltages they have online guides to diagnose the problem correctly Google the codes they tell you possible causes and how to test them but if you wanna burn money start downstream o2s then cats and go from there or cheap way out remove rear o2s from exhaust pipe block off holes with old o2s or a plug n zip tie sensors up under car.

It needs CATS. Unless you’re in California, Colorado or one other state, I can’t remember they’re not ridiculous anymore.

If you don’t have the cash right now, and they unbolt, and they’re borderline, I know people can get them to work for another year or so by soaking them in detergent for a few days.

Sort of like shaking a toner cartridge.

Check your 02 sensors take 2 min if you know how to use a scanner make sure they are switching correctly, then check your converters with back pressure probe or heat gun.

Any exhaust leaks before your 02 sensor will case same issue. Check these obvious problems first. Takes a few minutes.

The temperature going into your converters should be colder going in and hotter comings out.

A thermo camera will show restrictions as well. Make sure you have no other codes for the ECM as well. If so, what are they? To have p0420 and P0430 MIGHT indicate an exhaust leak. Any leak before the O2‘s will cause these codes. Keep that in mind. Even if you replace them with new converter assembly, you cannot have any exhaust leaks before you 02 sensor. And never go cheep with GM O2 sensors, you’ll chase your tail.