Originally Posted by oldskewel

There are many ways to actively get the ECU to turn the fan on, but for me it was easiest to command the active test using my foxwell. It spun it up gradually and then held it at full speed for a while before letting it back down. Prior to buying the new fan, I tested the system thoroughly to make sure the signal was being sent, but the fan was not doing its job. There is another thread on here where I provide a ship ton of info on that.

Of course, the foxwell commands go through the ECU, so if you really do have a problem with the ECU or the wiring, failure will not be conclusive.