Question about 2002 GMC Envoy

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Just replaced thermostat and now my fan clutch runs continuously

I just replaced my thermostat on my GMC Envoy with a 4.2 liter engine and now the fan clutch does not disengage. Could I have somehow messed up some other wiring like the temperature sensor that would cause the clutch to not disengage or does the fan clutch now need replaced again?

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  • Anonymous Dec 18, 2008

    I disconnected and reconnected the connection to fan clutch and it still will not disengage. I went to Autozone yesterday and had them plug in to the computer to get the codes and P1481 shows up, and I was told that I will have to go to the dealer to find out the problem. It also indicated that my cam position sensor problem and that the timing was advanced.

    Any suggestions? Please let me know. Thank you!

  • Barry May 11, 2010

    The fan clutch is electric, maybe you accidentally pulled the wire off when changing the thermostat. They are made to be fail save so if it looses voltage it will engage so the car dosn't overheat, check your wires closely.



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  • 1,224 Answers

Kirkasmann, P1481 is most definitely your fan clutch, it's very common on our platform. Only wires to check is the connection on the drivers side shroud. You said replaced "again"?. I've had bad ones out of the box, or it would tick tick tick. Buy a lifetime warrantly fan clutch for this reason, plus it's easy to do (as long as you cut a notch in the top of the shroud where the upper radiator hose is).

Posted on Mar 07, 2018


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Posted on Jan 02, 2017

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SOURCE: Replace the thermostat on 2002 GMC Envoy

4.2L Engine the thermostat and the neck where the hose goes on is one unit $25 at autozone

  1. Remove the necessary coolant from the radiator.
  2. Remove the alternator, Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
  3. Remove the thermostat housing bolts.
  4. Remove the thermostat housing from the engine block.
  5. Clean all of the surfaces of the thermostat housing.
  6. Clean the sealing surface of the engine block.

Posted on Dec 29, 2008

  • 57 Answers

SOURCE: A/C compressor/pulley clutch does not disengage.

It may be a bad low pressure cut out switch. You would have to hook the system to a set of gauges and look at the pressures. The low side should cut out at aprox.20 psi. if the switch is bad the compressor will keep running and ice up. The switch is easy to replace. It screws into the dryer (big silver can} it has two wires going to it. It's a cheep fix to try at home.

Posted on May 20, 2009

  • 5 Answers

SOURCE: Removing the fan clutch

get a big adjustable wrench and insert it in the bolt and hammer it fast in one blow that should solve your problem

Posted on Jun 04, 2009

  • 355 Answers

SOURCE: replace my thermostat

well do you have the 4.2 or 5.3 motor 6cy or 8cy need to know and i can help

Posted on Oct 05, 2009

  • 1311 Answers

SOURCE: How do I replace a thermostat in a 2004, 6

If you go to and do a search on thermostat replacement, you will find a thread that details the process.

Posted on Sep 09, 2010

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3 Answers

How much should I expect to pay to have the fan clutch and thermostat replaced in my 2004 Envoy?

The parts prices are $36 thermostat and depending on fan clutch model $88 - $260 From autoparts warehouse site
which leaves $580 for draining system and replacing parts and refilling system plus time a bit steep
get another quote from a different mechanic and decide

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do any of the radiator hoses colapse ? correct mixture of antifreeze and water? you might need to have the system flushed, Is sensor bad? replaced fan clutch?

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Your fan clutch could be going out...iin other words, it may be turning, appearing to be fine, but not fast enough therefor, not cooliing the engine enough.

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2003 GMC Envoy Service Engine light on. OBD2 Code is P0128

Ah the famous P0128.....It's 1 of 2 things. If your fan is not engaged constantly (would sound like an airplane or big rig everytime you step on the gas) and is working properly, that rules out the fan clutch. The other common problem is the thermostat. Replace the thermostat and the code will go away. Engine temperature needs to be at 210 degrees on these engines. If the fan clutch is constantly engaged, it's cooling the engine off constantly and won't get up to 210 fast enough. If it's the thermostat, it's stuck open and isn't allowing the coolant to properly heat up in time.

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2004 GMC Envoy.Check engine soon light is on the code for the trouble I am having is P0128. This means bad thermostat-it is not running hot, engine coolant temperature sensor which I had replaced,...

This code indeed does indicate a bad thermostat, but not in a way as overheating but the coolant temperature is not rising fast enough at warm up because the stat is always in the open position.

The rushing air sound you heard was most likely the electronic fan clutch starting to go bad. This is a common problem.

Nov 01, 2010 | 2004 GMC Envoy

1 Answer

1 have 03 envoy,6cyl,have replaced viscouis fan,fan still runs a lot, dealer has checked twice all ok

Do you have the check engine light on? If a fault code of P1481 or P1484 is coming up with a scanner, the fan clutch is bad.

Aug 22, 2010 | 2003 GMC Envoy

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2004 GMC Envoy with a P0526 sensor problem

This code indicates a problem with the fan clutch, the speed it is running is not the speed it was commanded to run/ The fan clutch assembly needs replacing.

Jun 03, 2009 | 2004 GMC Envoy

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Engine revs realy loud

You have a faulty thermostatically controlled fan clutch. Same thing happened to mine. As soon as you start the car, the fan is always turning, and the speed increases as the RPM is increased.

Oct 19, 2008 | 2006 GMC Envoy

2 Answers

Envoy 2002

You need to find a shop with a Tech 2 scanner. The pcm has to be recalibrated because when the fan clutch goes bad it back feeds into the computer and stores a hard code. And because the 02 is the first year for this style envoy its a pos! And these A**Holes from GM thought it was a good idea to have a electronic throttle body and gas peddle.


Aug 27, 2008 | 2002 GMC Envoy

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