Today I took the C5 out to go get haircut 25 miles to the destination. Everything was fine till i got into the car started the car and pushed the heater button on the hvac control unit.. No air blowing through the heating vents but I can feel slight air is coming through the vent but no pressure at all or blowing . The HVAC control unit lights are completely dead and the control button to heat, ac, any other buttons are not responding at all. Before 4-6 months ago heat/ac worked but would take 5-10 minutes before the hvac control unit would start working and hot air or air conditioning work and air would blow through the air vents. Also check engine light came on and I pulled the following codes:
P0134: Heated Oxygen Sensor(H02S) Circuit Insufficient Activity Bank 1 Sensor 1.
P0154 : Heated Oxygen Sensor(H02S) Circuit Insufficient Activity Bank 2 Sensor 1.
B0432 : Rear defogger relay circuit.

My engine is stock. Should I replace the two Oxygen Sensors? is the two sensors the upstream sensors on left & right on the exhaust manifolds?
Could something else trigger the O2 Codes besides the O2 sensors ?

Do you think my hvac control unit is bad that's why i'm not getting any air blowing through the vents? Can my Hvac control unit be repired?
As I stated my hvac control unit lights on the buttons, screen, on, off lights, etc are out. No function button working.

Any input appreciated in advance.

 

Whenever I see unrelated things not working on these cars like HVAC, O2's, Rear Defogger, Blower Motor I think of a faulty ignition switch...I actually have all these components highlighted in my FSM...there are 4 wires out of the ignition switch which feed all of these circuits...if you have and know how to use a voltmeter you can verify this when stuff is not working.

 

If the cars has 90-120k miles the stock o2s could be bad. At first with just headers my front o2s were working great no codes after adding headers i just hade the rear o2 codes and occasional air pump code pop up. After having the car tuned i started getting front o2 codes. Ive only put maybe 2k miles on the car since ive owned it 10 months and was stock except for a dual cone intake filter. I had front o2 codes pop up on my original ac delco o2s for bank1 heater circuit and bank 2 insufficient activity the same as yours. I changed them with some stock o2s from a higher mileage motor vehicles and both o2s were dead or read bad insufficient activity but didnt have heater circuit codes. I changed to amazon AFS75 and havent gotten any codes yet or last night when i drove it runs better then it did with the other o2 sensors. For me 02s are a maintenance replacement item at 100k miles with spark plug wires, spark plugs and other fluids. You could test the sensors and the plug to harness from the vehicle to confirm its getting correct power or readings. The two wires from the heater circuit or same color should read 12 volts with the ohmeter on them with their closed circuit with the key on and both signal wires should read 4.x on each signal wire with the negative probed to the header or frame.