Winter is coming another engineering wonder

3.0 · September 17, 2021

Got a 2020 3.0 D for the most part love the truck but not a lot of confidence in the engineers who take the bus and/or train to work. This is a heads up for the coming winter on your block heater.The engineers have put a thermostatic head in the male head of their GM specific block heater cord ( the cord is a rip off / 100 bucks if you have to replace it) so if you need to use another extension cord to plug in do not leave the plug head of the gm cord laying on the ground. If the air temp is warmer than -18c the ground may be colder opening the block heater circuit which the motor will see as a heat issue/fault code when you start the motor it will turn on the high fan for 6 hours of run time.The only way to resolve the issue is let the engine run in fan high for 6 hrs or remove the fault code. Gm doesn't think this is a serious issue and has shown no interest in resolving either the cord or heat sync issue so even though it's a pain if you come across this issue call roadside assistance and have them tow the vehicle to the nearest stealer and if it hits their pocket book often enough they will resolve the issue (put the thermostat in the standard male receptacle in the bumper) . Thought for the day ... think of how much more money GM would make if they did it right the first time?

SVG · September 18, 2021

I thought I remember reading that there was a software update to address the 'Full Fan Syndrome'?

Either way your point is spot on.

September 20, 2021

On 9/17/2021 at 7:47 PM, 3.0 said:

Got a 2020 3.0 D for the most part love the truck but not a lot of confidence in the engineers who take the bus and/or train to work. This is a heads up for the coming winter on your block heater.The engineers have put a thermostatic head in the male head of their GM specific block heater cord ( the cord is a rip off / 100 bucks if you have to replace it) so if you need to use another extension cord to plug in do not leave the plug head of the gm cord laying on the ground. If the air temp is warmer than -18c the ground may be colder opening the block heater circuit which the motor will see as a heat issue/fault code when you start the motor it will turn on the high fan for 6 hours of run time.The only way to resolve the issue is let the engine run in fan high for 6 hrs or remove the fault code. Gm doesn't think this is a serious issue and has shown no interest in resolving either the cord or heat sync issue so even though it's a pain if you come across this issue call roadside assistance and have them tow the vehicle to the nearest stealer and if it hits their pocket book often enough they will resolve the issue (put the thermostat in the standard male receptacle in the bumper) . Thought for the day ... think of how much more money GM would make if they did it right the first time?

GM do things right the first time. That's comical. I've seen enough with my truck to know that is not something they are competent enough to pull off.

redwngr · September 20, 2021

No need to be plugging it in at -18C (0F) anyway.

And yes, in late 2019 there was there was updated programming released to deal with the fan running thing.

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.