My 2006 Trailblazer is showing the P0495 Fan Speed High code. The light came on while towing a VERY heavy trailer up a steep incline in moderate heat. The guy at Autozone who read the code said their computer suggests a thermostat repair, but I suspect that it could have been high due to the load and the heat. Could this be the case? The fan sounds normal to me now, it's cycling on an off at a relatively normal interval.

 

the code sets when the pcm is commanding the fan clutch off but the fan is operating at high speed. this code by itself does not indicate a bad thermostat.