Cab harness differences from a gas to diesel on 2003 2500HD

[nickhavlat]

Is there a difference in cab harnesses from a 2003 2500HD with a duramax to a 2003 1500HD with a 6.0L? I did a cab swap and and swear I checked all the harnesses for likeness, but there must be something different in the transmission part of the wiring. It's an Allison automatic, 5 speed. My transmission temp gauge doesn't work, the tow/haul and OD off illuminate on the dash when selected, but have no effect. Also the line under the selected gear on the cluster does not illuminate. Dash has been checked and checks out ok.

 

Everything else on the entire truck works fine. I did find one wire on the diesel cab that goes to the instrument cluster that was not present on the gasser. I installed the wire and connected to the harness under the hood were it went to, but noticed no difference yet.

 

Anyone have any schematics or diagrams for what each pin or wire may do on the cab and transmission harness?

 

Thanks,

 

Nick

[nickhavlat]

Well I found the problem. On the entire cab harness from a gas to diesel, the only difference I can find is two wires. One is very important, the other not so much unless you need to see when your glow plugs are on.

 

On the C100 plug-in underneath the fuse panel under the hood, there are two wires that are on a diesel that are not on a gas. One is a blue wire which goes to your instrument cluster to show you when the glow plugs are on. The other is a yellow wire Class 2 Data Signal wire. This wire communicates through the network from each controller. This wire is the important one!!! Without this wire you have no tow/haul, overdrive off, driving lights are always on, no back-up lamps, transmission temp gauge won't work, and it also would not go into 4WD Low. There is another yellow wire two holes over from where this one should have been that is also a Signal wire, I put a jumper in from that one and everything worked!!!!

 

Not sure why GM couldn't spend 5 cents and just put the wire there instead of making two different harnesses. If anyone needs any help with wiring , I can tell you exactly what every pinout does and wire colors by connector now!!