2012 GMC Sierra cooling fan issue

jaded13640 · November 10, 2014

Hi guys, I've got a customer with a 2012 Sierra 1500 4x4 with the 5.3 that's having a cooling fan issue.

He says that the primary fan is not running and so the secondary fan runs all the time.

He says he's changed the relay. I assume he's referring to the relay in the fuse block.

I recall an Intrepid I had once that had a fan control unit down at the fans. It failed and both fans ran continously.

What could cause the this issue?

If the primary fan fails does the secondary fan run all the time or should it be cycling on and off as well?

I'm not familliar enough with this vehicle to give him a quote. Until I at least understand how that system works I don't know what to tell him.

I'm burried in work at the moment and would prefer to not have yet another vehicle sitting here until I at least know where to start looking for the issue.

I've searched my labor guides for clues and have come up empty.

Any help would be greatly appreciated.

Thanks,

Wayne

00Silverado4x4 · November 10, 2014

Fuses good? Proper relay replaced? Was the relay he replaced the correct part? Power going to fan? Does fan have a good ground? Is there any problem in the wiring, loose, melted, disconnected?

Unfortunately you need to take a look at it prior to being able to even start troubleshooting such a problem.

gmtech4 · November 10, 2014

you know better ,scan it

8.1HD/ALLISON · November 10, 2014

Scan it. Get wiring schematic and circuit description before you even start.

jaded13640 · November 11, 2014

What I'm asking is this, Is there a controler for the fans other than the relay in the fuse block? Is this a common issue with these vehicles?

You know how this goes, someone calls, tells you what it's doing and asks you how much to fix it. I didn't give him a price or anything, I wanted to do a little research first.

I've got limited parking here at my shop and at the moment, EVERY spot is full. I just want to get an idea of what I'm looking at before I have him drop the truck off.

06sieraz71, like I said, I don't have it here yet. I'm just trying to get an idea as to what might be going on, what common issues are with this vehicle and that sort of thing before I have him bring it out. And to give him an idea of what we're looking at cost wise. I know that sometimes can't happen. I know sometimes you have to do a search and destroy mission to figure out what's going on. But sometimes it's a common issue and the forums are useful.

govtech4, as I understand it there are no trouble codes. And again, it's not here yet for me to scan. I'm looking for tips and ideas in advance of getting here and checking it out to maybe help speed up the process of elimination.

8.1hd/allison, Yes, I will scan it but he tells me there's no check engine light. And yes, a diagram would be extremely useful. Do you have one or a link to one? That would be very helpful.

Thanks to all that replied, Again, I haven't got the truck here yet, I'm doing research in advance of it coming here and to try to give the guy a rough idea of what this is going to cost him to fix it. Unfortunately people have gotten accustomed to being able to call around to shops to "shop around" for the best price. This probably isn't one of those deals. This is probably going to be a hands on diagnosis and not a "oh, yea, it's the canootin valve and will cost you 200 bux" kind of thing.

Thanks again,

Wayne

Badbird2000 · November 12, 2014

^{_{This may be way off, but I remember in my 2000 T/A, I was sitting in traffic one day and it started heating up quick, like near 240.. I was near the dealer so I pulled in. A plastic fan had wrapped around one of the fans, so it couldn't spin at all. Keep in mind, this was in Florida in the summer. I would hope the owner would look at something that obvious right up front..}}

newdude · November 12, 2014

Some food for though...

Cooling Fan Control w/o HP2
System Overview

The engine cooling fan system consists of 2 electric cooling fans and 3 fan relays. The cooling fan relays are arranged in a series/parallel (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.

Low Speed Operation

The ECM applies ground to the coil side of the cooling fan low speed relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the low speed relay. The left cooling fan is connected in series to the right cooling fan through the de-energized series/parallel (S/P) cooling fan speed control relay. The result is a series circuit that operates both fans at low speed.

High Speed Operation

The ECM applies a ground to the coil side of the cooling fan low speed relay, the S/P cooling fan speed control relay, and the cooling fan high speed relay. When energized, the high speed fan relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan relay and the S/P speed control relay provide ignition voltage and a direct path to ground for the left cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans operating at high speed.

Two codes can set, P0480 and P0481. Relay or motor are most likely culprits unless there is a wiring issue. The motors can be somewhat common.

jaded13640 · November 13, 2014

Some food for though...

Two codes can set, P0480 and P0481. Relay or motor are most likely culprits unless there is a wiring issue. The motors can be somewhat common.

Newdude, excelent stuff. Thanks for taking the time to post it.

Wayne

2010CREWCAB · September 15, 2015

I am Having a Simular issue, Currently the Primary Fan is blowing the Fuse, In the begining it wasnt working so the secondary fan was running non stop, which was extra loud. so the other day i found the Fuse and replaced it, fan came on for about 10 minutes then fuse popped. Today I checked all the wiring and everything looks good, Im at at standstill on what to do!!