Which means that when you lock the diff the ECUs get the low input so when the transfer case is in high the engine ECU goes to the low gear fuel map and the engine is overfuelled also the SLABS ECU doesnt know that the diff is locked to addapt it's activity to that unless you spliced into the diff-lock input circuit too...
do you see the diff lock warning on when you lock it?
If by TQ you mean traction controll on a 2004 you dont have to cut any wires. However, if the SLABS doesnt know that the diff is locked the TC would work normally if needed but not needed too much with locked diff also in some rare cases TC and locked diff can come in a "conflict" and make things worst.
So run separate wires for the diff lock only for that particular circuit and for low input use a switch on the console to use it when you select low gear otherwise the whole management is mixed up and even if you think it works well it's not.
