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2003 GMC Envoy:
4 Failed Electric Coolant Fan Clutches

Alex Steele
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seen in Truck Trend



I own a 2003 GMC Envoy XL with 4.2L 6-cylinder engine. I live in Beirut, Lebanon, which is in the Middle East (Asia).


I have had a repeated problem with the cooling fan clutch (4 failed clutches in eight months time), so I decided to switch to an electric fan setup. As I live outside the USA I have no access to kits available in the US for this. I used an electric fan from a Mercedes-Benz S class car with a fan speed controller, a thermostat and A/C control. The system works fine except for one problem, which is, because the original fan clutch and fan are removed the "Service Engine Light" remains lit.


What can I do to trick the Envoy's computer into thinking that the fan is still there? Or is there a setting that tells the computer to forget about the fan? Do you know of any company that sells a part that hooks to the fan clutch plug to mimic the presence of the clutch?


I get the feeling that the Envoy's mileage is suffering due to the service engine light remaining lit. I was told that when the service engine light is lit the Envoy would not drive properly as the computer switches into limp mode.




I don't know of any way to mimic the presence of the fan clutch. The "Electro-Viscous" fan clutch actually emits a fan speed signal to the Powertrain Control Module.


And yes, when the service engine light comes on the powertrain control module will use default control parameters to prevent damage to the powertrain and get you home safe. What I don't understand is going through 4 fan clutches in 8 months. I know it gets hot in that part of the world, but there's gotta be more to the story.


You may want to go back to the original fan clutch, or a combination of both. A standard coolant fan clutch is thermostatically controlled and engages the fan according to underhood temperature. An electro-viscous fan clutch is very similar but controlled electronically by the powertrain control module.


The powertrain control module determines engagement (fan speed) once analyzing data including coolant temperature, A/C refrigerant pressure, vehicle speed, intake air temperature, transmission fluid temperature and ambient air temperature.


Check with a GMC dealer or customer service on related Technical Service Bulletins which may help with your repeat failure problem -- there are several. They cover issues such as fan clutch wiring harness damage causing a service engine light, A/C performance and a ticking noise.

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12 Jun 2018, 08:55
RE: Bennie Lee, Yes the fan noise is normal at start up for a few minutes. This is because of a newly designed fan clutch. The noise may be loud at times but is perfectly normal. As long as you don't have a check engine light and the vehicle isn't overheating it is considered normal operation.
Bennie Lee
11 Jun 2018, 10:35
Replaced fan clutch of 2003 GMC Envoy, but noise remains for a few blocks, is this normal with a new clutch?
04 Feb 2010, 21:27
To all Envoy owners, especially with a 2003 with 4.2L 6 cylinder. I went thru 600.00 dollars worth of parts; cooling fan, water pump, thermostat, etc, and still overheated. Take an advise from an old timer in GMC mechanics, the radiator cap lost its pressure and was giving me all the headaches. Change it. 17 bucks well spent, and no more problems. Try it.


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