so my check engine lite came on in my 2000 blazer, so i had auto zone scan the codes
1) knock sensor, i knew it was gonna throw this code i have a 2001 engine in my 2000 knock sensor not tapped in the block yet.

2) p0410- secondary air injection system

3)p0300-random cylinder misfire

4)p0135-heated oxygen sensor bank 1 sensor 1

i already replaced secondary o2 sensor bank 1 sensor 1 still getting code and already replaced the secondary air pump (smog pump) any idea y im still throwing codes for these? are they all related to the mass air flow sensor?
im lost and getting aggrivated

 

Swartlkk has an awesome post here:
https://blazerforum.com/forum/tech-articles-diy-29/posted-obdii-trouble-code-diagnosis-26408/

 

More specifically:
P0135 - HO2S Heater Circuit Bank 1 Sensor 1
P030x - Random/Multiple Cylinder Misfire Detected
P0410 - Secondary Air Injection System

Also, you may want to run a search for each individual code as they have been discussed before.