2018 Silverado

[frustrated andy]

I have a 2018 Silverado 5.3 the check engine light stays on ,code 420 and 430 . I have replaced the exhaust (y pipe back) and the sensors , I've replaced the spark plugs and wires light is still on and reading the same codes. Need help with it 

[rav3]

Did you ever clear the codes?

[frustrated andy]

I've had code cleared several times by machanics the light comes back on in just a few miles.. ????

 

[CamGTP]

Those are cat codes, did you actually replace the cats themselves?

 

You typed you replace the y-pipe back, does that mean the y-pipe itself or the cat back?

 

And did you go with OEM or aftermarket?

 

If aftermarket they usually set a check engine light. You can try to space the rear sensors out of the exhaust stream some to not trip the code.

[frustrated andy]

Yes new y pipe and cats , muffler all new system and it's oem parts 

[rlcole321]

Now did you replace the exhaust parts "Because" of the codes, or for another reason?, your mechanic should be able to read the DataStream to see if the O2's are within their respective ranges, like upstream O2's should fluctuate between .100 to .900 vdc rapidly, and the downstream O2's should stay high about .700 to .900 vdc all the time (with veh at temp.) Did you replace any O2's?  You can buy a fairly good OBDII scanner to read this data at fairly low prices.

[newdude]

Check the air box and air filter for proper sealing.

 

Check the exhaust for leaks.

 

If its all good, then I'd say the new catalyst might not be broken in or was ever broken in.

 

See HERE - MC-10156912-9999.pdf (nhtsa.gov)

[frustrated andy]

The truck has went into a safety mode because of the catalytic converters codes. I've called a Chevrolet garage to come get the junk . 

 

[CamGTP]

Cat codes themselves should never cause reduced engine power, I've never seen that before.  A different issue surely could though.

[frustrated andy]

Plugs 6 &8 showed misfire and another one for ruff ideal and the cat code put my 2018 Silverado in safety mode .