No trailer lights 2000 tundra 4x4 4.7

I'm very lost, checked main fuse ( tow package equipped) replaced the flat 4 plug all new wiring and lights on trailer that work correctly ( CHECKED WITH OTHER POWER SOURCE) , NO POWER TO CONNECTOR ON TRUCK ? Any suggestions?

 

Was there power at the fuse?

 

The 4 pin connector should plug into a 6 pin connector a short distance under truck Do you have voltage at the 6 pin connector ?

Are you having any issues with any other systems since trailer circuit is part of other circuits covered by approx 5 fuses.

 

No voltage and no other system issues. All fuses are good in both fuse panels.

 

We can only go by what you tell us and can only assume you have double checked your self, especially your voltage readings at the 6 pin connector.

Given the 6 pin connector I mentioned above is part of the Frame Harness, it's definitely odd that you did indeed not have no voltage there.

If you are positive there is no voltage at T 6 connector, and "no other system issues. All fuses are good in both fuse panels", my next suggestion is to look at the 12 pin connector(BB1) under the drivers seat.
That connector is the feed for the Frame Harness that feeds the connectors shown below.

 

I didn't think the older 1GTs had tow package?

If not, I'd expect this to be spliced in. And if that's the case, I'm going to expect someone scotch-lok'd into wires, and as is inevitable with scotch-lok style wire-manglers, there's one or more compromised wires.

 

My "tow package" was me adding a V5 rated hitch and the Curt wiring adapter plugged in between the rear harness plug to add the 4 flat. There is not a way that I know of to just splice into the wiring on these, an adapter is needed. Added a 7 pin round plug at a later date for trailer brake controller, had a buddy at a shop do it.

 

Ah yeah, I've seen those. If that's what OP is doing, I'd be pulled off the harness and testing continuity of the wires inside the adapter harness with a DMM, then.

 

They started offering optional tow packages on the 2003 MY(V8 only), according to the brochures.

 

I have one of these at work, and it's awesome!

$25 CURT 58270 7-Pin RV Blade Trailer Wiring Towing Vehicle Socket Tester, Black

https://www.amazon.com/CURT-58270-Vehicle-Socket-Trailer/dp/B001EOWQY4?smid=ATVPDKIKX0DER

For 4 wire, there's this:

$7 True Mods 4-Way Flat Trailer Wiring Tester [Nickel-Plated Copper Terminals] [Male & Female] [Continuity Test] 4-Pin Trailer Light Wire Circuit Tester

https://www.amazon.com/ONLINE-LED-S...ds=trailer+light+tester&qid=1692992824&sr=8-5