Yeah but ISTA doesn't just test on an off functionality. Also with my Launch it tests the whole system. The sensor tested good also during activation tests. The system as a whole turned on and off like it should be. That's why this is so puzzling because with the capabilities of ISTA and my Launch I should find the issue but everything in the system is good. I guess when I doing the cooling system refresh I can install a new fan since It is 16 years old.

 

If you disconnect the PWM signal and the fan still turns on, its a bad fan.

 

I was just reading how the coolant temperature sensor and also the a/c play a part in it.

If the coolant sensor is disconnected (or faulty or intermittent) the fan will turn on high (uncontrolled).

 

I finally found out why the fan comes on at startup. Apparently since the aux pump was a knock off when the car does it's initial check it triggers the fan. Its just like when you install LED side markers and the car does a check at startup the lights flicker. I exchanged the pump with an OEM one and it stopped.

 

I'm pretty sure you didn't install that knockoff part, right?

 

The brand was right but it was a knock off. They looked exactly the same and around the same price. The Amazon seller got me. Lol. I got the money back so no harm no foul.