how to get 05 sieera truck fan to activate

[mr blizzard]

Lost our 05 engine last spring re antifreeze and oil cocktail lol

Finally we found a needle in a hay stack, an 03 engine, over the course of several weekends in the driveway we swapped the 2. Everything is amazingly good EXCEPT the electric fans wont come on, the electric fans are original 05 part

 

Replaced temp sensor still no luck, all codes are clear but it is sensing the engine is cold when its not, just been doing small trips around town''

 

Any easy fix like a relay etc, to all the back yard mechanics and full time thx in advance

John

[mr blizzard]

Sorry it is an 05 gmc sierra 5.3

[DanD]

What does the temp gauge read on the dash?

If the gauge is functioning that tells us the the PCM (computer) is receiving and properly interpreting the coolant sensor's signal. Both the IPC (Instrument panel) and the PCM use the same sensor signal (kind of).

The PCM will not turn the engine cooling fans on until engine temperature reaches approx 98C (210F) and then it'll only turn on the one fan. At approx 105C (210F) then both fans are commanded on by the PCM.

If the truck has a functioning AC system; the one fan would be commanded on as soon as the AC pressures reach a certain pressure.

Without a proper scan tool, there's no other way to force/fool the PCM to turn the fans on.

Has the truck actually overheated?

Get your hands on one of those infrared thermometers and test the actual temperature of the engine. Princess Auto sells them for about $25.00. Take temp readings at the upper and lower hose to engine connection housings.

You may have a thermostat that's stuck open and the engine has not reached the cut point for the PCM to command the fans on?

If the engine is actually getting hot enough for a fan request; you should be able to hear one, two or all three relays click on. If so then it will be time to see if one or both fans are getting power. Use a test light connected across the two terminals of the disconnected cooling fans (both) connectors; one at a time. The engine will need to stay running; the PCM will shut fans off when engine is turned off. If the test light lights; then you likey have burnt out or seized fan motors. Again if the test light lights, plug the fans back in electrically and then lightly hit the fan motors with a small hammer (Don't beat the crap out of them) Sometimes the motor"s brushed will get stuck and not make the internal connection to the armature; this light tapping may jar them loose and get the motors turnning again?

I know more questions then answers and now that I've likely confused you completely; try and answer the ones you can.

 

Dan.

Edited September 17, 2015 by DanD

[mr blizzard]

To Dan

Wow so much appreciated, lots to think about, I will go out and check it again tomorrow, getting hammered by a wicked chest and sinus cold, and of course Biaxin what the dr prescribed yesterday is currently not available in this great town

I will check it out and thx so much Dan for your input

[davey buoy]

To Dan

Wow so much appreciated, lots to think about, I will go out and check it again tomorrow, getting hammered by a wicked chest and sinus cold, and of course Biaxin what the dr prescribed yesterday is currently not available in this great town

I will check it out and thx so much Dan for your input

Yes Dan is on that,I actually know this stuff as well.Let it idle for a bit,get the thermometer ,check both hoses as said,than at least you will know if the motor may be overheating and stop before damage. Great ,easy advice right there from Dan.

[mr blizzard]

Thanks Davey bouy, good advice, oh to have a town with biaxin and a Princess Auto lol

[mr blizzard]

hey dan. this is this guys son. Im working on the truck. The code I get off the code reader is po118. This is saying the "engine coolant temperature circuit high input". Now it still says this after I replaced the coolant temp sensor. My buddy was saying to check the relays (replace if I have any kicking around) and then try it again. Ill take the truck down the highway for 5 minutes, sense its getting warm, pop the hood and then disconnect the sensor. The like a whirlwind both fans come blazing on, I look at the temp gauge in the truck you can watch it spike right up to about 3/4 hot then instantly fall right down to the 75ish mark (lowest setting) on the dash. I will see if I can round up some relays and go from there. if that doesn't work the other option is to gut the electric fans and put on 1 big clutch driven fan like some other models had, which will delete this issue. Ben.

[davey buoy]

I.m thinking like Dan here,have you changed the thermostat yet?,Does your rad have a lot of the fins folded over?.

[mr blizzard]

Davey bouy we replaced the thermostat when we replaced the engine, the fins are totally straight no folds

[Freshtrax]

Simple fix it to run the power from the fans to an ignition hot power supply ie . Daytime running lights ect . That way the fans would always be on while the truck is running and the thermostat could do the work from there. It's a fix that would get the truck back on the road until you track down the gremlin.

[mr blizzard]

Thanks Freshtrax, never thought of that

[huzzsaba]

I would suggest starting with replacing the thermostat again in case the one you replaced is faulty and then make sure to get all the air out of the system by burping the system when filling. Not sure if these engines have a bleed valve. If it does make sure to bleed the system of air.

Also check to see that all wiring related to the cooling system and fan are plugged in.

Edited September 18, 2015 by huzzsaba

[DanD]

hey dan. this is this guys son. Im working on the truck. The code I get off the code reader is po118. This is saying the "engine coolant temperature circuit high input". Now it still says this after I replaced the coolant temp sensor. My buddy was saying to check the relays (replace if I have any kicking around) and then try it again. Ill take the truck down the highway for 5 minutes, sense its getting warm, pop the hood and then disconnect the sensor. The like a whirlwind both fans come blazing on, I look at the temp gauge in the truck you can watch it spike right up to about 3/4 hot then instantly fall right down to the 75ish mark (lowest setting) on the dash. I will see if I can round up some relays and go from there. if that doesn't work the other option is to gut the electric fans and put on 1 big clutch driven fan like some other models had, which will delete this issue. Ben.

 

Are you sure that it's not you that's setting this code P0118? If you unplug this sensor with the engine running for any longer then 20 seconds, this code will set. The PCM will go into a form of limp in mode and command the fans on. The PCM also defaults to 80C which in turn drops the temp gauge in the dash to just off the cold mark. When you say that you can sense the engine is getting hot; what does the temp gauge say?

Don't bother with the relays, you say the fans come on when you unplug the sensor; so we know they're OK, along with the wiring to the fans and the fan motors themselves.

I would like to know what the voltages are on the signal return wire, at the temp sensor connector. Ignition off disconnect the temp sensor; turn the key on engine off (KOEO) measure the voltage at the signal wire (yellow wire) it should be around 5.2 volts. Making sure that the ground lead of the multi-meter is connected to a known good ground.

If the voltage on the yellow wire is way above the 5.2v start looking for a short to power. If voltage is way below 5.2v start looking for a short to ground or an open in the circuit. Open meaning a broken or corroded yellow wire; somewhere between the sensor and the PCM.

There's more tests we can do but let me know these results before going any further. Depending on what you tell me, we may need to stat back probing the PCM and disconnecting the PCM to continue the test.

 

One last thing make sure that the engine is actually getting warm/hot. Let it sit & idle, it can take up to 20 minutes before a fan request can happen. If the engine does actually starts to overheat; you know what to do; UNPLUG THE COOLANT SENSOR LOL or have a hose ready and soak the rad down, until the engine cools. Driving down the road there's air flow through the rad; so even on a hot day while driving the fans will rarely come on. Not unless there's a mechanical issue causing the engine to become hot.

 

Dan.

[Old Ironmaker]

I had to laugh when I read "give the fan motor a tap with a hammer". I am no mechanic when it comes to cars, I never have been this all sounds like rocket science to me. But the funny thing is I had a similar problem and I tapped it with a small hammer to get it to work. That I can do. When in doubt smack it!

 

Good luck on the truck Blizzard.

Edited September 18, 2015 by Old Ironmaker

[DanD]

Yea I know what you mean. LOL

You should see my electronics work bench; scan tool, oscilloscope, multi meters, amp clamps and a HAMMER!

To tell you the truth there is a prescribed test that all manufacturers use; it's call the tap test. You connect up the oscilloscope to lets say a mass air flow sensor, start the engine and then hit the sensor. If you see a glitch in the sign-wave replace the sensor.

 

Dan.

[mr blizzard]

huzzaba thanks and we will try another, even new parts can be defective, thx

 

Ironmaker, thanks for the encouragement, Dad was a mechanic for 35 years at Dehavilland, and of course new one or two things about car engines lol,,,when I got my first car a used one he had a gift wrapped box for me to celebrate, not really his style ,,when I opened it up there were 2 items , a hammer for hitting the starter and a wooden dowel, the dowel would be placed against the alternator or water pump and you would place your ear to the other end,,,the reason to check for excessive bearing noise, still have them today lol

 

Dan D have a great weekend, tear off a couple of caps for me

Really appreciate your help, seriously, going to a garage is out of the question right now and besides we just hate to give in We can handle some mechanical like engine and tranny replacements, little hard to do on gravel driveway but our electrical abilities certainly have room for improvement but with your willingness to share your expertise I am sure we can solve this issue, my wife son and I thank you

 

And all these years on the board I thought you just fished and added comments to the board :tease:

thx John

[DanD]

My Dad always told me that I'll learn more by listening (reading here) then talking out of turn; that's why my post count after all these years is still below a 1000.

I only post when I can add something to a thread or try and help someone.

Other then that; my story telling skills are not all that good.

I'm kind of like Joe Friday (Jack Webb) from the 60's Dragnet show; "just the fact ma'am just the facts" LOL

 

Dan.

[manitoubass2]

My Dad always told me that I'll learn more by listening (reading here) then talking out of turn; that's why my post count after all these years is still below a 1000.

I only post when I can add something to a thread or try and help someone.

Other then that; my story telling skills are not all that good.

I'm kind of like Joe Friday (Jack Webb) from the 60's Dragnet show; "just the fact ma'am just the facts" LOL

 

Dan.

???

 

Ill just post about anything ???

 

Im no mechanic either, mind if I pm you dan with a question?

[Old Ironmaker]

I would use my flashlight and put the working end against a line to listen for flow or on fluid drive couplings etc. for small clunks. When I did that with our new Plant Mgr, he asked the GF if I was pulling off one of my antics? It works to boot.

[HTHM]

I would use my flashlight and put the working end against a line to listen for flow or on fluid drive couplings etc. for small clunks. When I did that with our new Plant Mgr, he asked the GF if I was pulling off one of my antics? It works to boot.

You!? Antics!!!! I would have never thought that.

[DanD]

 

Ill just post about anything

 

Im no mechanic either, mind if I pm you dan with a question?

 

Ask Away.

 

Dan.

[manitoubass2]

2002 jeep liberty 3.6 litre

 

Spedometer wont work.

 

It kicks on and off.

 

Abs light is on even after being serviced 2 weeks ago so im thinking a wheel sensor???

[manitoubass2]

Oh and i just replaced the alternator before being serviced

[irishfield]

Jeep speedo is the speed sensor on the rear differential, or more likely the wiring harness from it to the body is either chafed on the emergency brake cable or broken. It gets 12 v in and puts out 0.8V (if I remember correctly) back out to the computer as it counts teeth on the sensor wheel on the ring gear.

 

This one drove me nuts and in the end was determined to be the sensor pin to socket connection was a loose fit.

Edited September 21, 2015 by irishfield

[manitoubass2]

Thanks dood!

 

Ill have a look