AUX Auxiliary Fan not working but its not the FAN!

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BMW X5 2004 3.0 E53 – NOT A BAD FAN – CIRCUIT PROBLEM!

HELP! My electrical Aux fan doesn’t work and my car overheats now in the summer.
HAVING WIRED IN A NEWTEST FAN – I KNOW IT’S NOT THE FAN ITSELF. CAN’T FIGURE OUT WHAT’S WRONG – HELP PLEASE!
I did NOT remove the existing fan. Thank god - an awful job. I just tested a new one.

My repair steps: Here are paths I’ve taken:

Tried laying a new fan on the engine (uninstalled) with pos and neg wires. Didn’t work. I assume that the third little black wire in that cluster of 3 (sensor wire from the DME) is holding me all up. (Might be wrong, but it’s my guess.) Have not tried to test that 3rd wire as it needed an oscilloscope or something.
Also, I have a hole in my cat, not sure if that’s contributing. My Bentley manual says that Cat temp could be a factor, but not sure.
Final Stage Resistor inside under dash – I replaced this last year, but it could be bad.
Fuse – 50 amp is not blown in Glove fusebox
A/C pressure switch on A/C line– jumped the pos and neg posts for continuity and while car off, there’s continuity. Did not get any continuity from the 3rd terminal. I think it's a combo high/low sensor.
Both cooling temp sensors in the hoses were just replaced 3 months ago. Assume, correctly and good, but may not be true
A/C does blow cold once the car moves. But, if standing still, A/C gets warm and the engine gets dangerously hot. I have to turn engine off when hot. The A/C gets cold slowly even if I am driving at higher speeds. I have to toggle the snowflake switch once or twice to get cold.
I’m at the point of trying to figure out if it’s the ECM (engine control module, located in the engine EBox) or DME or a sensor. ANY THOUGHTS?
How to know?
HELP! I can’t figure out how to get this to work! Anyone know?