I you're talking about blower speeds 1 and 2 not working, then it's the resistor. Instructions on how to replace it are here:
http://www.automotiveforums.com/vbulletin/showthread.php?t=175159
fuel systemfor 1998 chevy malibu
what is the cost to repair password for antitheft system chevy malibu 2001?
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if im not mistaken the heater control has vacuum lines. take off heater controls and see if you have a bad vacuum line to heater box.
Find the source and repair it.
It just cost me $350
You can't repair an o2 sensor,You'll half to replace it
Traction Control
Body Control Module
check heater fan to see if it is working.
Begin by removing the wiring harness. Remove the retaining screws. The emission control will come off. Reverse the process to install your new emission control.
How do I repair heater that won't shut off in 1998 chevy s-10 zr2 pickup?