Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Something is not right with the information you provide: if there was power on three legs and nothing on the Green wire, that would mean the relay is internally shorted and also that there was power on the Light Blue wire feeding the fan motor. Would you please recheck and get back to me so we can continue?
Sorry, that's still wrong. The Light Blue wire is the one that connects to the fan motor; if it had power, then the fan motor would be turning. The two Red wires are the ones that supply power to the relay.
OK. That means the onboard computer is not grounding the relay. From this point on we need a scan tool capable of reading engine data that would allow us to see if the computer is receiving a signal from the coolant temp sensor and, if it is, what the heck it's doing with that signal. Basically, it's either that or guessing, which I don't do.
I'm sorry, I'm not familiar with solus ultra scan tools, but if it is the equivalent of a Tech-II, then you should be able to command the fan on and see the results of that command on the screen. So...
... if it shows that is being turned on on the screen, but there's no ground at the relay Green wire, then there must be an open in the Green wire from the PCM connector C1 terminal 43 to the relay.
... if it doesn't show on the screen to be turned on, then the computer is bad.
... if it shows that is being turned on and there is ground at the relay wire, then check for power at the relay Light Blue wire. If no power there, replace the relay. If there is power on the Light Blue wire at the fan motor and the motor still won't work, then check the Black/White wire at the fan motor for ground. If ground OK, replace fan motor.