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Nein7Oh posted a topic in Operation and Maintenance: 450 Model, 2005-2006, dieselSo I just did the external relay modification to solve the headlight and fuel pump issues. Miraculously she (gf owner) has working low beam headlights, and the car starts. It runs better than I've seen it since she bought the car. Unfortunately now the car won't turn off. I can turn the ignition switch to the off position and remove the key (in neutral) and the car will keep running as long as the brake pedal is depressed. Obviously you just need to take your foot off of the brake once you've parked and the car can be driven normally. That's not good enough, and I would like to find the solution before I make any other improvements. My thought is that the fuel pump wire that I ran out of the SAM has been pierced by one of the solder joints pertaining to the brake light circuit. In the meantime the brake lights function normally. I would think that if they were in contact, the brake lights would be on as long as the fuel pump is running, or some other sort of malfunction. I have read that the brake light switches on the 450s are problematic, but I don't know how the two issues could be related and why it would manifest after the other issues were resolved. A side note is that I can now communicate with the car via the OBD2 port. It had previously lost that functionality and I thought that the OBD2 reader had gone bad until I tested it in a different vehicle and it worked fine. I know I SHOULD start by taking the SAM apart again and checking for a pierced wire, but if I do that I will be inclined to remove the wiring that I used and resolder a smaller gauge wire. Frankly I don't want to do that if the problem lies elsewhere. I am currently using 14 gauge flat speaker wire. It is truly flat, they braided it similar to a ground strap. It is really cool old school hifi car audio cable. 14 gauge is definitely overkill and I could probably get away with 18 gauge and a hot glue gun to keep the wire in place as I route it around solder joints (probably what most sane people do).