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I am swapping in the 5.3 from the Tahoe into the TJ. I have re-worked the GM harness and am ready to install it.
The problem I have is with getting the Jeep's factory gauges to work. There are six that need attention:
Speedometer
Tachometer
Oil Pressure
Water Temp
Battery/Voltage
Fuel
I will limit this thread to one - the battery/voltage gauge
I need some clarification on the wiring and PCM. For clarification, the Jeep's sensor connector is not compatible with the GM's. It is not a plug. The wires run to a "junction box" that has terminals that bolt onto the alternator. (See image.)
The Jeep's wires are:
Generator field source (+) (PCM Gray C25)
Generator field driver (PCM White B10)
Ground
The GM's wire are:
Generator field duty cycle signal (PCM Green 75)
Charge indicator control (PCM Green 15)
Ground
1. Does the alternator need to be connected to the GM PCM for it and the engine/PCM to function properly?
2. If not, since I cannot connect the Jeep's alternator connector to the GM alternator, can I wire the GM alternator sensor connector to the Jeep's wires that run to its PCM - Generator field source and Generator field driver wires? Hopefully, this will trigger the gauge?
3. If so, can the Generator field source and Generator field driver wires be spliced into the GM's wires so they connect to both the GM's PCM and the Jeep's PCM?
Or, any other variation to get the volt gauge to work.
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Wiring Harness - Will this work? 
