I've recently acquired an LS swapped '95 Silverado. Someone else did the swap. All factory gauges on the dash work except the engine coolant temp gauge. I have already ordered the '98 Camaro 3 pin ECT sensor that will feed the 411 PCM, and it has the extra pin (Green wire) for feeding the gauge in the dash.. However... I can't find the green wire!!!! Does anyone know where under the hood I can find that green wire? Where does it pass through into the interior? It looks like whoever put the engine in did a good job of wrapping up and looming all wiring.. I will have to open it all up and hopefully be able to find that wire. I was just hoping that someone could tell me where that wire comes through the firewall so I can start looking there and work my way forward. YES, I searched ALL wiring diagrams on-line and NONE of them show the underhood/engine mounted sensor that sends signal to the temp gauge. They ALL show the YELLOW wire from the 2nd ECT (mounted on top of intake) that goes back to the old (now non-used) ECM.. If anyone knows where the wire for the Coolant temp gauge comes through the firewall, I would appreciate the info.. Will help me with my search!

 

I’m not totally familiar with the process for an LS swap, but if the PO took the time to carefully wrap the harness, maybe the original wire was removed altogether? If you remove the cluster, is the wire present at the cluster connector?

The only places I’m aware of where the factory ran wiring through the firewall was at the front left corner near the booster and on the opposite side, right about where the fender liner and the firewall meet. Being a gauge wire, I’m fairly certain the wire would’ve had to have been routed to the left side.

I’ll try to find you some info but I need the following info to properly build your truck on pro demand (it’s unlikely to matter but I’d rather be sure).

What was the original engine in the truck?
Is it 4wd?
Extended cab?