I've had my 2002 discovery 2 with 127k miles on it for about a year now. Neglected severely by previous owners, so I've done quite a bit of work on it including recommended maintenance for it's age. Has all the common issues, some of which I'm still sorting out, but one problem is stumping me. The passenger side front turn signal comes on during braking, not like blinking, but just solid anytime brakes are applied, but the driver side does not. I replaced driver side bulb thinking maybe it was supposed to come on, but it's still not. Turn signal works though.

So are they supposed to come on during braking, or no?

 

So they are certainly not supposed to come on during braking! I wonder if you have an exposed wire somewhere that makes contact as it shifts forward under braking, or does it come on even if the vehicle is stopped? I'll dig up the electrical diagrams for you (if you haven't already done it download the RAVE, Electrical Diagram, and Electrical Library PDF's) and see if there is any wierd crossover that could happen between the brake lights and the passenger turn signal. I can't think of any off the top of my head but the Lucas electrical system never ceases to amaze me in these things!

 

OK, I have the start of an answer, but you're probably not going to like it. According to pages 81 and 85 in the circuit diagrams the passenger side tail lamps and the passenger side turn signal share the same connector/header (C0289) which is located under the passenger foot well (picture attached). An exposed wire in the loom or contact in the connector between the two would cause one to trigger the other. Do another test, you know that the brake light triggers the turn signal, but does the turn signal trigger the brake? If you turn on the turn signal and the brake light flashes at the same rate as the turn signal we can be reasonably certain that a connection is somewhere in the loom or connector. Another question, is there a difference in tempo between the driver side turn signal flash and the passenger turn signal flash? Often times (although I'm not 100% certain on the D2) the rate of flash is determined by the current draw of the lamps, this is why a burned out lamp blinks faster so I would assume that there would be a difference in tempo if you passenger side was driving the turn signal and the tail lap. The tough part is that there are a LOT of wires in that loom and connector, the turn signal wire is Green/White and the Tail Lamp wire is Red/Orange so that should help you narrow it down a little.

 

Appreciate the reply. I won't be able to dig into it until this weekend most likely but it activates whenever the brake switch is activated and the brake light doesn't flash with the signal on nor is it blinking any faster or slower than the other. Not the first time I've had to dig around in that area but I'm curious as to what I'm gonna find. Might end up following the wires all the way and see if anything is fishy and checking out the diagrams.

 

Doing some more testing now and it's not just the front turn signal lighting up when brake switch is activated, it's the rear turn signal and the side marker on that side also. Digging around right now to see if i can find anything out of the ordinary in that bundle of snakes under the passenger side dash.

Looking at the back side wiring I remember that there is trailer wiring harness connected back here. Almost thinking someone hooked it up wrong. These didn't come factory with a trailer light hookup installed did they? There's a curt box tucked up in back underneath and it's also got a curt hitch on it.

 

Solved it. It was the trailer wiring harness. Someone either installed it improperly or the box went bad, but I got it cut out and everythings working as it should now. Now I just need another trailer wiring kit.