None of the GMT 400s ECMs have that ability. You would have to have done the 411 swap to do that, or so I have been told.Why aren't more of you using the PCM to control the fan? You can have a hysteris with the PCM, choose your own on/off, have it turn off at speed, and have it turn back on at speed if you're overheating. It can run based off of AC pressure, and can control duals in either a series parallel configuration for hi/low speeds or just on/off.