1992 Ram no overdrive

Hi, I've got a 1992 Ram 150 5.2L 2wd with about 210k. I haven't had overdrive for quite some time now, and I'm finally getting around to trying to fix
it -- truck shifts well other than that. I'm hoping its just a wiring problem, computer has the overdrive solenoid code and the o/d on/off button on the dash will not light. I want to hook the solenoid directly to power to test it but I don't know where the wiring for it is. The Haynes manual doesn't mention it at all. I thought that it was the orange/blue wire on the tail housing, but that turned out to be the speed sensor. The only other plug I can find is a three prong that I believe is just neutral safety and reverse lights. Does anyone know where the wiring for the o/d solenoid inputs into the transmission?
Thanks
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The three-wire connector is on the drivers side, behind the shift lever, facing up. The three wires are blue, green and black. The blue center wire is the keyed power, green is the OD control wire and black is the LU converter control wire. The SBEC (computer) grounds the green and black wires to activate their respective operation; if there is power at the blue wire when the key is ON, grounding the green wire should engage the OD after the 2-3 shift has occured.
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