My truck is starting hard and idoling rough and wants to die occasionally. It's finally throwing me a number 12 and 15 code. Can you guys help me with these codes and what I need to replace or fix for these

 

OBD codes

 

Thanks for the guide, it definitly helped me out. After I replaced my coolant temperature sensor, my Blazer it running like a Chevy again. No more rough idle, no hestitation, or stalling out. I got my power and torque back. Thanks brother.

Respectfully Straka

 

Any time