What can cause a high cooling fan speed error in a 2002 Trailblazer?

: Either a PCM reprogram or the fan clutch asembly will fic this condition. Replacement of the fan clutch is very labor intensive, and it is easy to put a hole iin the radiator or break something else if you do not have experience doing this procedure. TechJK

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These errors are caused by software problems in the PCM. General Motors warrants this defect for unlimited mileage. Take your vehicle to a dealer for a free PCM upgrade to correct this and NUMEROUS other concerns (stalling, high idle, high fan speed, shift problems)

This is garbage- GM will tell you get real- totally rubbish. The problem lies in their monopolized parts (Dealer stock item only) Common problem - expensive part (entire fan assembly) and labor- (entire front end disassembly) I paid appx. $600.00 for this error code to be cleared. Good luck!

EVERYONE SHOULD BE AWARE THAT IF YOUR PCM FAILS IT IS COVERED UNDER THE (LONG TERM) EMISSIONS WARRANTY. YOU DO NOT HAVE TO PAY TO HAVE IT REPLACED. IF THE DEALER WANTS YOU TO PAY FOR A NEW PCM THEN CALL THE 1 800 NUMBER FOR CHEVY (ON THE WEBSITE)

This two answers helped me a great deal. I had the exact same problem on my 2003 Trailblazer. The check engine light came on, I took my vehicle to autozone and they told me the code was P0495 (cooling fan speed high)but they did't know how to fix the problem. After loking at this two previous answers, I called the dealer and they told me that it would cost me $89.00 to reprogram my PCM. I took my vehicle to the dealer and before checking my vehicle, the mechanic noticed the noise my vehicle was making (like a jet engine) and told me that in addition to reprograming the PCM I needed to replaced the fan clutch. The total cost was going to be $747.00. I didn't have the money so I went home and looked on eBay. I purchase a brand new fan clutch for $130.00. I am not a mechanic and it took me about two hours to replaced the fan clutch. You need a 12" crescent tool to remove the fan clutch from the water pump pulley. After replacing the fan clutch, I was on my way to the dealer to reprogram the PCM but noticed that the vehicle was working great so I skip the dealer and went to the 7 eleven and got me a six pack to celebrate. My vehicle is working like new. I hope this could help somebody out there. Good luck

I have the EXACT same problem. My local Chevy dealer wants to charge me $800 to repair! I looked at the fan clutches on eBay (ZBRA) for $130. I noticed they have an electical connection but I couldn't quite see one on my clutch fan. Am I just not seeing the connection or is it possible that I don't have one. If I don't have a connection, is there a place to plug-in the new one? ALL 2002+ TRAILBLAZER/ENVOY/BRAVADA/SAAB 97X ETC HAVE A FAN CLUTCH ON THE I6 ATLAS ENGINE AND THERE IS ALWAYS AN ELECTRICAL CONECTOR TO IT. LOOK FOR A DANGLING WIRE THAT MAY JUST CONNECT TO A PLUG ON THE SHROUD.