Although I have never dealt with this issue, the alarm ecu on a 96' is located under the dash on the passenger side (NAS). It is a green box about the size of a pack of virginia slims cigarettes, mounted with a couple lock nuts through plastic ears on the case. I found mine after it broke the ears off & fell out from under the dash. (I had removed the dust cover years ago) I remounted it with velcro (the fabric of our lives) and have had no problem since. I would guess that the antennea is one of the 400 or so wires that run out of that box. Hope this helps, LRWheelman
I just replaced my antenna/security ECU. The failure was the cause of a lot of inconvenience. I seem to remember a mention of an antenna extension recall but can't be positive. The recall was to extend the wiring on the antenna to increase the range of the key fob. I'm still waiting for the second keyfob to come in so the dealer can re-program the security ECU.
Here's the TSB about the inadequate range. I'll ask the German tech about it when I go back for reprogramming. I think the fix was to add a wire to the antenna and run it up into the dash under the windshield to extend the range. I'll keep the forum posted.
TEC861496 DEC 96 Security System - Antenna, Inadequate Range
Check your fuses, too. I just replaced a burned out one tonight that I'd never really noticed before. I don't know what it does, but apparently it's been burned out since before I got the truck, because after I replaced it, the lights started flashing when I pushed the button (I didn't know they were supposed to do that), and my transmitter range was greatly increased. I can lock/unlock from inside the house, woohoo!
I remember doing the antenna updates a few years back. They were easy. The new larger antenna wires into the original connecter pin as the old one then you run the new larger antenna along the front of the dash. The new larger antenna works much better.