Originally Posted by
Jon S.
The later GMPP calibrations will cause the fan to operate constantly once initially activated, unless the ECM sees a vehicle speed of 15 MPH or more. This was done by GMPP to prevent the fan from cycling on and off at a stationary idle.
There is obviously a parameter for this, but it is not available in the software.
Also, I never thought to check for a "timer" when I had access to one of these vehicles.
As a test, try placing jack stands under the rear axle (block the front wheels - safety first !). Then drive the rear wheels to a speed of 25 MPH or so. If the fan stops nearly instantly (if below the temperature threshold), then there is likely no timer. If there is a delay in the fan turning off, repeat as necessary to determine the exact number of seconds delayed.
With this information to work from, perhaps HPT could add these parameters.