how to control fan timing GM

[teamjin]

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what is mean red box and yellow box?

[87skier]

These are percentages that the computer uses to set the "state" of the cooling system. To control the fan speed the ecm works like this:

Read the coolant temp.
Look at "Desired % vs ECT" table, and find percentage that matches ECT.
Look at "State vs Desired %", and find state matching percentage.
Look at "Output Control vs State" and determine output control from state.

Turn on fans matching the output control.