We have a 2003 XC70 which a few months ago had an instrument cluster failure. At first it was intermittent, but for a while now has been just plain dead. It might be related to this post.

We also noticed our lower 2 brake lights and night running lights were out, but the top 3rd light did work when brake pressed. I checked the bulbs with a multimeter - they were all good on left and right. I checked for power at each bulb socket when the brake pedal pressed, but didn't see any at either left or right side.

I then checked the 2 brake light fuses at the rear REM...they were good. I looked for power on the fuse contacts when pedal pressed, but say nothing. There are 3 relays as well for brake lights. At this point I swapped one but it didn't help. The 2 other relays are behind a trim panel. I got to those later.

Anyway, I ended up disconnecting the battery to see if the REM module in the cargo area needed a reboot. When I reconnected the battery the left brake light and running light was stuck on and the right were both still off. Turn the car off and the left lights go off.



See Pic below for where I am at now...


I tried pulling the 2 brake light fuses and the 3 relays individually to get the left tail lights off when the car was on and running, but the lights stayed on? I then pulled ALL of the 2 fuses AND the 3 relays, and the left lights were still on. Funny thing is, if I pull a fuse and check voltage across it, I see nothing? I tried with both brake light fuses, but not the relays. I then tried pulling the bar shunts at the REM and found that when one of the 4 was removed, the left lights went out.

I would consider the possibility that I have a short at the left rear tail light assembly, except for that it wasn't working at all until the battery disconnection test.

Any thoughts?