I have a 2002 Chevrolet Trailblazer Lt and received Code#PO495 on the diagnostic scanner. Manual said's it's "Fan Speed High".

Any one ever had this issue before or have any idea why and what to do? please help..

what it is refering to is the hydro/electric clutch fan on the ft of the motor. It has an electronic selenoid in it that changes the fluid flow to lock the clutch up. It uses a hall effect sensor feedback system to give info back to the PCM on actuation.

most of the time it is a bad connection or water in the connection at the 4 wire plug to the fan. look there first.

make sure the engine fan fuse (10 amp) in the engine compartment fuse box is ok.

make sure the ground to the relay is good. It is found on the lower left side of the engine block.

if all that is ok, you have a choice. you can take it in to get checked properly or take a gamble that the fan is bad and replace it. You are as far as you can go, because the feed to the relay is a pulse width modulation signal and without a scope, you are stuck.