I have a 2001 Supercrew that did not have the tow package. I installed the OEM 4/7 pin wiring harness and the 2 missing relays on the sticky note. However, I can only get power thru the turn signals on either connection and the taillight pin on the 7 pin is always hot. I can't get power on any other pins. The truck had the harness under the dash for the brake control unit and the connection works fine. Am I missing a relay or wire somewhere?

 

Looking at the truck 7 pin connector the 11 o'clock position is the park/running lights.(Brown with white trace) It should only be on when the lights are on. If you have auto lights it might be on when you turn on the truck.

9 o'clock is left turn/brakes (Yellow)
3 o'clock is right turn/brakes (Green)
1 o'clock is the aux charge line and only on when the key is on (Orange)
Center Pin is reverse lights (Brown with green trace)
5 o'clock is electric brakes (Blue)
7 o'clock is ground (White)

With an OEM harness the wires should be the same on both ends. If they are the same it should be correct. Something sounds off in your description. Re-check the ground as well with a meter. If the ground is bad weird things happen in these computer controlled trucks.

One last thing....are you checking truck function with a trailer plugged in or a meter/test light?

I highly recommend using a meter and/or test light to check function to eliminate a huge variable.

 

Thanks for the reply. My multimeter had a fatal accident, so I have been using a test light at the pins. Will get another one and check the resistance of the ground circuit. Your thoughts about the ground make sense. The trailer is a 6 pin horse trailer. I have a 7 to 6 pin adapter and originally suspected that was where the problem lay. But when plugged in, I get exactly the same readings as using the test light on the pins.