2012 W900 left brake light

[Truckdriven]

Wow Rawze nailed it on this one! I finally got the truck back to the shop today and started testing all the chassis node inputs according to the pinout sheet while the light was turned on and found a wire with approximately 2 volts. Also thanks to mikanic for clarifying how many inputs there are. Then came the fun part of finding the bad spot! As much as I do not like to probe through wire insulation that's what I ended up doing about a foot in front of the crossmember that has the chassis node mounted behind and voltage was good so I opened up the harness and soon found a hole corroded in the wire. I will attach a pic. Cut the bad spot out, put adhesive lined heat shrink over my probe hole, soldered the wire back together and all works correctly. I would have thought I would have a low input voltage fault but only had a low output code, so obviously when these nodes act up ALL input voltage wires need to be checked. My gut was telling me the node needs replaced since there was no input fault but as always the proper testing saved a lot of wasted money! Again thanks to all for your advice!