If your car is over heating both fans should be running, both fans should also be running if you turn the A/C on. Try the A/C if only one fan is still running there is either a problem with one of the three fan relays or the fan motor itself has gone bad.
There is a 50 amp maxi fuse (#7 in 2nd diagram) which powers both fans on two different circuits. This fuse is located in the engine compartment and neither fan would run if this fuse was blown. You can easily check each fan for power with a test light. Right fan has power on light blue wire and Left fan has power on black wire.
The ECM commands when each fan comes on. It does not command both fan unless A/C is on or excessive temps are reached. If both fans were always on the car would cool too fast and harder for the ECM to keep it within operating temperatures.
Images (Click to enlarge)
Friday, October 21st, 2016 AT 3:50 PM