Okay, so I installed my initial tune in my P59 ECU, originally from an 03 Yukon. Nothing changed in the VCM suite on the tach settings. My aftermarket tach worked with the factory tune but does not work after uploading the edited tune. Now has a tach circuit code.
Connected the white "Engine speed" wire (green connector, pin 10) to tachometer signal wire.

Any ideas? I've read about installing the resistor to boost the signal but if it worked with the factory tune, why would I all of a sudden need it with the custom tune?