Join Date: Aug 2005
Location: Arlington Texas
The AS up and down sense wires go into a plug above and over to the left of the brake pedal and switch. You will find a body to engine junction there, it is a bunch of plugs held on to a common plastic carrier and the carrier is held on by a single 10mm bolt. You add the wires to the white (Service Manual says natural) connector. One side of the harness (socket side) has the AS sense wires already there, the other side which is the plug with pins has the wires missing. You add the two pins in the spot according to the diagram.
Ground can easily be tapped at the driver's seat bolt or from the shift bezel lighting ground (splice required here). The shift bezel lighting ground wire is where I got my ground.
Power needs to come from a wire that is on when the car is on. The orange connector in the interior junction block (NOT BCM, the BCM plugs into the JB) has some fat wires carrying power and a few skinny ones. The one at pin 7, if I remember correctly, has the fused ignition switch output you need.
If you get the parts from TFC, it will come with a diagram.
I'll see if I can do some digging.
2004 300M Special...257K miles. Original powertrain!