3.0 Duramax Egine Fan Stuck on High

3.0 · January 11, 2021

I've got the Baby D and when I plug in most times the engine fan cuts in on High and will not shut down the only fix so far is to clear the code or to let the truck sit for 6 hours.Just had it stuck on high yesterday and drove around to see what would happen.The fan would not shut down and the temp gauge was sitting at 1/2 it's normal position.This was at 0 c or 32 f (wonder what would happen at -25c) . Has anybody had this issue and has it been resolved,what was the fix?My service dept and apparently GM say there is no known issue and yes I've seen the GM techlink from dec 2019

redwngr · January 11, 2021

Immediate fix -- don't plug it in unless is below 0*F (-18C)

According to this from 13 months ago there is an update coming --- don't know if it's released.

I've been running 6.6's for many years. They live outside and get started every day. The are never plugged in. Frequent winter temps 0F -10F.

I have no intention of plugging my 3.0L for those temps either.

This is it's first winter. So far coldest start was about 16F (-9*C). Started just like the middle of summer (except the glow plugs operated a little longer.

https://gm-techlink.com/?p=12389

Cooling Fans Running for an Extended Period

December 13, 2019

Some 2020 Silverado 1500 and Sierra 1500 models equipped with the 3.0L diesel engine (RPO LM2) (Fig. 12) may have the engine cooling fans running continuously for an extended period of time. The Check Engine MIL also may be illuminated.

Fig. 12

Currently, an engine calibration in the Engine Control Module (ECM) will falsely set DTC P0111 (Intake Air Temperature (IAT) Sensor 1 Performance), which occurs when the engine block heater is used in ambient temperatures above 0°F/–18°C. As a result, the cooling system will go into remedial action and turn on the cooling fans at 100%. The remedial action will continue until the engine goes through a six hour cold soak.

If this condition is found, clear the DTC and return the vehicle to the customer. Do not perform any further diagnosis or replace any related components. An updated calibration will be available shortly.

Also inform the customer to avoid engine block heater use in temperatures above 0°F/–18°C. While the owner’s manual states an engine block heater should be used in temperatures less than 0°F/–18°C, it isn’t vital until much lower temperatures of less than –13°F/–25°C.

Chrisd534 · January 31, 2021

Suffered this issue twice and having it happen for a third time. I have yet to plug mine in and I still suffer from this. First 2 times dealer said they couldn't find a problem and just reset the computer. Don't want to waste my time for a 3rd time going to the dealer. Pretty annoying having the fan run on high when it's - 15 out and the engine not being able to get up to temp because of this

3.0 · January 31, 2021

It sets a code when it happens don't clear it ,they found a sensor and thermostat issue on mine finally

Claudia · December 26, 2021

Ive got the baby D as well and same thing happening.. When i plug in my fan stays stock in high speed.. and its -25 .. the température is at 1/2.. if anybody knows how to fix this other then clearing the code everytime let me know..

Chrisd534 · January 20, 2022

So I've officially had this happen for a 4th time now except this time I used the block heater. Temps went down to - 30c overnight so I plugged it in. Following day fans were on 100%. Made an appointment with the dealer and just got it back this evening. I put the s&b intake on between the 3rd and 4th cooling fan issue and now the dealer is trying to blame the issue on the maf sensor extension harness with the s&b kit. I think I need a new dealer or gm is just a joke it's been 2 years with this issue and still no fix

John Smolinski · February 19, 2022

2021 silverado 3.0 duramax diesel started engine temperature 4 degrees Fahrenheit cooling fans on high service emissions on reduced power in 170 miles the block heater was not used

redwngr · February 20, 2022

On 2/18/2022 at 8:20 PM, John Smolinski said:

2021 silverado 3.0 duramax diesel started engine temperature 4 degrees Fahrenheit cooling fans on high service emissions on reduced power in 170 miles the block heater was not used

Let us know what they find.

Clearly that's not normal.

Clearly they don't all do that.

Richard McDonald · April 13, 2022

I have a 2021 Silverado with a 3.0 diesel. I have 623 miles on it. When I started up at 65° F radiator fan when on high speed and the check engine light came on. Took it to the dealer they reprogrammed it. 50 miles later it is doing the same thing.

poppy510 · April 14, 2022

On 4/12/2022 at 5:32 PM, Richard McDonald said:

I have a 2021 Silverado with a 3.0 diesel. I have 623 miles on it. When I started up at 65° F radiator fan when on high speed and the check engine light came on. Took it to the dealer they reprogrammed it. 50 miles later it is doing the same thing.

My 2022 Sierra did this once. 70 degree F weather. Turned it off and it came back on normally. It threw a code that self-cleared after 2 or 3 starts.

DemonWorks · April 16, 2022

It sounds like there are multiple issues going on in the replies. There are certain codes, that when set, the computer goes into a fail safe and runs the fan.

I'm not saying, nobody has a problem, just that there are multiple different issues here.

As to the S&B intake being blamed... that was a tech not wanting to work on the vehicle... that's some BS for sure.

Oleshka · February 20, 2023

Have 2023 gmc Sierra 1500

cooling fan working non stop without any codes, outside is 25 degrees

superdashdad · February 23, 2023

My '23 did exactly what is described in that 2019 tsb when I plugged it in at -5f. Its been over 3 years and they have not fixed the problem yet.

cdrgoose · January 17

I have purchased a used 2020 AT4 with a 3.0. I have had diesels for well over 20 years. Always plugged in when it was freezing or lower outside temperature. Never a problem. Why did they change things soo much with these now generation Diesels? Anyway, I also had that fan issue running at 100% when it's 15 degrees outside. I had it plugged in when I started it. Clearly in the manual it says to unplug it prior to starting. Something I've never done before. And no error message. Go to my destination, fan still running at 100%. 12 hours later it's back to normal. Back at home, plugged in for the evening. Next morning, I unplugged it first, then started it. No fan on, and continued to run normal. Second day same thing, unplugged first, fan ran normal. So just an opinion, it seems that the issue in this case, is only because of starting it prior to unplugging it. Starting it after unplugging it seems to work properly. Just putting this observation out there. Happy trails.

gemarsh · January 18

11 hours ago, cdrgoose said:

I have purchased a used 2020 AT4 with a 3.0. I have had diesels for well over 20 years. Always plugged in when it was freezing or lower outside temperature. Never a problem. Why did they change things soo much with these now generation Diesels? Anyway, I also had that fan issue running at 100% when it's 15 degrees outside. I had it plugged in when I started it. Clearly in the manual it says to unplug it prior to starting. Something I've never done before. And no error message. Go to my destination, fan still running at 100%. 12 hours later it's back to normal. Back at home, plugged in for the evening. Next morning, I unplugged it first, then started it. No fan on, and continued to run normal. Second day same thing, unplugged first, fan ran normal. So just an opinion, it seems that the issue in this case, is only because of starting it prior to unplugging it. Starting it after unplugging it seems to work properly. Just putting this observation out there. Happy trails.

I've been plugging diesels in since the early 70's. I was always told to unplug cord before starting. Reason was so cold coolant that might hit the hot heating element wouldn't shock the element and ruin it.

Doubt it would, but why crawl out of a cab after starting to unplug cord.