So I removed the panel below the glove compartment to get some leaves out of the blower fan and decided to check all the connectors on the SLABS module to make sure all were firmly connected. They were but then I noticed this wire with electical tape on the end right by one of the connectors. I looked it up in RAVE electrical library and circuit diagrams. The connector is C0504. I unplugged it and checked it agaist the connector details in the manual. I unwrapped the electrical tape and the wire(which was green with a brown stripe) still had the connector on the end. Per the connector diagram, this wire is supposed to be position 7 on C0504. The schematic shows this wire going to ECU-SELF-LEVELLING/ABS (SLABS) (D163) and then to header 0287. It looks like maybe it has something to do with the reverse lights? I'm hoping someone better versed in these schematics might be able to tell me what this wire controls and why someone might have pulled it out of the connector. Thanks in advace!

 

Pages 4.67 and 4.70 of the D2 Electrical Library confirm your suspected pathway:
...the feed is connected to the contacts of the hill descent relay,,,. The feed [is also connected to] the starter inhibitor/reverse lamp switch (automatic gearbox vehicles). When the switch is operated, the feed is connected on a GN wire, through header joint C0287 LHD/C0294 RHD, to the SLABS ECU pin C0504-7.
The two pages in both cases are referring to the Hill Descent Control -- one page for the SLS system and one for the ABS system. If you don't have air suspension then that system is irrelevant. Either way, it looks like someone disabled your HDC for some reason?

 

I appreciate the reply. Yes, no air suspension. Seems very strange that someone would disable the Hill Descent Control. I guess I will try try to reconnect the wire and see what happens. Hopefully it doesn't cause any problems or trigger any warning lights.

 

Sounds like maybe an idiot way to cure the three amigos? Better check you dash lights to make sure they all work. Turn your key to position one and see if they all light up. I bet there are other things they did.

 

The dash lights do work. In fact I had the 3 amigos when I bought the truck. The Option B repair had already been made but one of the plugs to the ABS modulator was not fully seated. Once I fixed that and replaced some bad hubs, the amigos were gone and still are. I do wonder the same thing: that pulling the wire was someone's misguided attempt to fix the amigos.

 

what year is your disco?

 

It is a 2004.

 

UPDATE! I re-installed the wire into the connector. All was fine when I started the truck and went forward. I put it in reverse and still fine until I actually moved the car in reverse. Then the HDC failure light (amber) came and stayed on. I turned off the ignition and restarted the truck. Again no lights on even after putting it in "D" and driving forward. And again putting it in "R" caused no lights but then driving in reverse made the HDC failure light come on. I guess that explains why the wire was removed. I would really like to fix this the right way. Any thought on how to diagnose and repair this issue?