I had then same problem on my 02 SE. After removing the glove box I found the electrical connection to the heater control valve loose. After pushing the connection "in" the control turned the valve shaft as designed.
P0336 CKS code with tach dropping to zero from 2000 then erratic. Code occasionally will clear then reoccur. Loss of power when climbing hill. Never stalls always starts. 160,000 miles. In park, MAF shows steady increase in lbm/min when increasing rpm