CEL wire

[Ackattack]

I'm finishing up the LS engine swap on my 90 K3500. I'd like to use the CEL in the dash. I believe the wire that comes from the ECM is tan/white (I'll have to check my wiring diagram that's in the shop). Anyways, how is this wire routed? Does it go through the firewall, across the back of the engine, and then back in near the fuse block, or does it run across the dash?

Right now I just have a little LED wired up and it works fine, but I want a clean look. (Also, for some reason the factory CEL is on....not sure why )