Hey there! First and foremost I wanted to thank you all for your previous help some months back. Not sure if this is new problem or recurrence of mis dx'd one but here it goes:

My S40 is generating OBD codes P0128 and P0117. In April 2010 encountered P0128, followed y'all's excellent advice and replaced temp sensor and thermostat with resulting resolution of issue. Within last 10 days with average outside temp < 35 degrees I'm experiencing a radiator fan that runs after engine stop (didn't before), marked power loss on acceleration from start (better after adding fuel injector cleaner and HEET) but persistent P0128 and P0117 codes (latter being newly encountered). In addition the dash temp displays pegs within 3-5 minutes, drops then pegs and stays. I get hot air from heater. Admittedly I went cheap on the aftermarket sensor and thermostat but really....8 months? So it's January in northern Illinois and my dad is understandably reluctant to service my car in our unheated garage. Open to all reasonable suggestions.

Jess