Cooling Fans Running for an Extended Period

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.


– Thanks to Robert Bastien

Printing to a PDF File in GDS 2
Extended Engine Crank Time


  1. simon ofoegbu ibekwe says:

    Petrol engines do same what do we do next .i have witnessed it on 2015MY GMC Yukon. Cooling fans continue to run for an extended period when engine is swiched off, and the battery almost ran down.
    Equinox does same. Why?

  2. I sent in a PIR on this exact same condition about 2 separate vin’s on December 6, 2019 and I never received a response back. I am glad the info is out now on this. I advised the customer at that time to not plug in vehicle above -18 deg

  3. So the engine block heater isn’t thermostatically controlled not to turn on over temperatures above 0°F/–18°C as was the case in previous years?

Leave a Reply

Your email address will not be published.