trailblazer lt ext 2005, engine light

Hi,

I have tb lt ext 2005,

The truck is working good and the engine light is OFF.
BUT a/c was not working anymore, A mechanic diagnost a bad clutch fan.
Clutch fan was changed, brand new.
As soon as part is installed, A/C started to work.
But as im leaving the garage the engine light went on.
The mechanic said , I will unplug the battery for 5 minutes for reprogramming.
This was tried, and seemed successful, engine light went off.

On my way back home, engine light went on again.
Next morning, truck wont start, engine light is on. no power going to ignition.
Tried starting it for 5 minutes, then it starts, engine light still on.

Any ideas?

tk's

get it scanned and let us know the error codes.

hi again just got the code,
p0526 sensor fan speed circuit,

anything i can do or a mechanic?

p.s. code was removed, and it came back after truck was restarted,

does this error code could prevent truck from starting?
for couple of time, upon turning key to start, it kind of drop dead, for few seconds, retried few times, then it starteds..

The usual cause of this is a bad connection at the radiator cooling fan or the electrically controlled cooling fan is bad.