Got PO300 code

[Mudsport96]

They do have 4 O2 sensors. 2 post and 2 Pre cat. There are multiple codes with different P numbers for 02 related problems and problems that cause sensor to hi/low limits of rich and lean. Ill concentrate on the codes that relate directly to 02 sensor defects. no sensor output or heating element open on sensor and/or no voltage to heater element. 02 sensor has to be real hot to give valid readings and that is what its internal heating element is for. If the cat(s) were bad I would expect to see a code for a bad cat and that code is generated by using the values of the pre and post cat oxygen sensor readings. There will be a substantial difference in readings between the 2 with a bad cat this in between them. Ive got 2 K chassis (Denali and Tahoe) very close to 300k miles and original cats. Sounds like OP jumped the gun buying cats and that was an expensive mistake.

Over 400k on the original cats here. But always maintained so they are good. Perhaps the OP had another issue that killed cats and may happen again. Or, his crank sensor is flaky and is okay at idle but bad above that. Hopefully, he gets back to us after the parts replacement.

 

[Mudsport96]

My english is not so good, but as I understand, you think that i'm right.

We in Germany would say:
"Er schoss mit Kanonen auf Spatzen"
What means free translated:
"He shot sparrows with cannons"

I love this saying.

 

[latvius]

Replaced converters, sensors and CAI filter, runs fine.

 

[03yukXL]

For what it’s with my 2003 had the same code and issue. Ended up being a failed intake gasket. They get old and harden, then lean air causing a leak condition

 

[latvius]

For what it’s with my 2003 had the same code and issue. Ended up being a failed intake gasket. They get old and harden, then lean air causing a leak condition

So one day you lost power driving then the next day it worked fine?

 

[03yukXL]

Not entirely sure because when it happened I limped it to a safe spot and got it fixed. Didn’t wait for it to come back