04 TB temperature needle drifts to the right when going up a hill

gica

Original poster
Member
Dec 25, 2012
135
Cali
I expect this is just a typo/mistaken numbering,,, but it would be 2 & 4 to be jumped...
Yes sorry about that the 4 and 2 adjacent ones. But what could cause all of the fans I have used to not respond to commands? I mean the pictures in my post shows the different fan speeds as opposed to expected levels. It cannot all be bad fans.
 

aaserv

Member
Dec 1, 2019
408
N of Baton Rouge, La.
All this might be posted already but the control of the fan speeds are done by the PCM via the 3 other wires that go to the fan. Might ck connections on those. White and Black(grd)
run the fan. Grey is a 5 volt supply and gry/white is the reference signal from the fan sensor inside the fan. There is also a Dk Blue involved. all 3 of these go back to the PCM which then feeds the wht/blk wire at the fan relay to regulate the speed. Their is an article somewhere on the site that explains all of this and the testing procedures. I had it printed out but cant find it, Ill keep looking and try to get it up here. 1 thing further is the response is not instant but can take several minutes sometimes at various RPM's.. The article mentioned explains all that...
 

gica

Original poster
Member
Dec 25, 2012
135
Cali
Great if you can find it would be great. I have spent a lot of time and some money on this car, its sole purpose is to pull a 20' boat and without the boat it is great unless ambient temperature is above 105 then it starts to go up above 220. If I drive the boat same issue at above 90 degrees. other than that the car runs awesome. I just replaced front and rear struts, front and rear rotors and pads plus e-brake pads. Not to mention the 6 year ordeal with P0440 code that ended up being the gas tank inlet valve. But before I did that I replaced everything in the system. So if I can do something to reduce temps would be great but if that is the way trailblazers act in high ambient temps then B-it.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I don't remember what brand you used but it was determined that most, if not all, aftermarket clutches, including Hayden, don't work as well as the OEM part from ACDelco (Hella/Behr). Also, a lot of these aftermarket ones do fail early. Our go to used to be Hayden but it was determined by @JayArr that it didn't perform as it should.


So we now recommend using only the original OEM part, especially if having overheating issues or towing.
 

aaserv

Member
Dec 1, 2019
408
N of Baton Rouge, La.
There is a factory software update for the 03-04 models to solve overheating conditions. My understanding is they updated the fan speed controls for 05+ and this software update brings the 03-04's up to date. Ive been wanting to have mine done for over a year but havent gotten around to it. If you go to this web address and put in your VIN it will give you all the updates that are available for your truck. https://tis2web.service.gm.com/ The 1 for the fan clutch issue is listed under PCM/VCM Control module. It gives you the part numbers and everything for the updates. Mine (also an 04) came up with 4 pages of available updates to all kinds of functions....But the main 1 I was interested in was the overheating problem. The 1 for updated shift points is probably a good 1 as well. Im going to try to go ahead and get these done soon.
Im still unable to find the detailed article on diagnosing the fan clutch but if you look at the service manuals listed on Moosemans profile there is the original diagnosis papers listed under 04 engine cooling that should provide a little more understanding of how it all works. You do need a shop quality scan tool to go thru all the steps however. Ive battled this problem for 2.5 yrs and think I solved it now by installing an original BEHR factory fan clutch that came on these cars. The 1 have on it has over 200k miles on it but it has worked properly although Im still a few weeks away from the 95-100 degs days that will really tell the tale. Drove it today with temps around 89 degs and needle held firm at 209 the entire way. I still run my electric fan at stop lights and bumper to bumper traffic.

Another thing you may try....i pop my hood and then click it down but dont completely shut it. Leaves about a 1" gap in the front. Yea Im scared to death my hood is going to fly open if i hit a railroad crossing or a big bump but so far so good. I dont know if this helps at all, could make it worse i guess but its something to try as we're grasping at every straw...
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
There is a factory software update for the 03-04 models to solve overheating conditions.
:iagree:
That is a good point that I had completely forgotten about since I don't have anything older than '07 now. Heck, I should check anyway for my current trucks for anything updated just in case.

If you can find someone with a Tech 2 or a J2534 compatible tool or interface to update your PCM, it doesn't have to be done at the dealer, but then even a dealer should be able to do it in less than an hour.
 

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