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Do you have a wiring diagram and a voltmeter or 12 v test light with a reasonable knowledge of how to use it?
Let me look into the wiring diagram and we will start with testing the running light or taillight circuit. Just to clarify you do have daytime running lights.
In order to diagnosis we will have to check One thing at a time one step at a time. Locate the fuse block on the right side of the instrument panel center console area. This is basically where the passengers left foot would be. Locate that panel and identify the fuse box the top left fuse is the taillight fuse with the taillights turned on you have 12 V to that fuse? Just north of that about 3 inches is the taillight relay it is the second relay up on the left. Does that relay click on when you turn the taillights on? Click this link and download the illustration.
When you turn the taillights on the first click on the light switch can you feel the taillight relay click on and do you have 12 V to the taillight fuse?
That does not add up. If the relays not clicking there should be no power to that fuse that relay supplies power to the fuse then out to the lights. I'm going to opt out at this point. This probably is going to be a hands-on type repair some things just can't be tackled very easily in this type of format. This will open the question up so that if anybody has run into this type of problem before where there has been a security system added then they might have additional information for you.
Hello. Please allow me to assist on this. My colleague Skyvisions is very correct in his line of diagnosis. You have now added that the tail fuse blows every time you engage the lights. Is this correct?
Ok. Let's do this. On each corner of the vehicle there is a marker light, plus the license lights. The wires to these lamps are Solid green and White with a black stripe. Disconnect every one of the 6 wire connectors and place a new fuse into the panel and re-engage the lights; see if the fuse blows again