Just bought 2000 Blazer and took to Autozone and they pulled the above 3 codes. for the P0360 I replaced the Ignition Coil. for P0440 not sure what it means. Something about a vacuum. for the P0155 it says heater condition (heated oxygens sensor Bank on Sensor 1).

Should I replace both oxygen sensors? or both.

 

swap the o2 sensors around. see if the problem follows. most likely just a bad sensor.
p0440 is a very small evap leak. could be the gas cap

 

I had a p0440 come up a few weeks back an pick up a new gas cap an haven't had it come back up yet.

 

thank you guys

 

Here are the code descriptions & links to the diagnostic procedure (if currently available):
P0155 - Heated Oxygen Sensor Heater Circuit (bank 2, sensor 1)
P0360 - Ignition Coil J Primary/Secondary Circuit
P0440 - Evaporative Emission Control System

You can also search for the codes themselves to see what other members have run into.

I would definitely suggest swapping the O2 sensor to the other side (B1S1 location) to see if the code changes to P0135. If it does, then the sensor is bad. If it doesn't, then I would suspect a problem with the wiring.