At a loss here and hope FTE can help.

Vehicle is '03 F150 XL 4x4, 4.6/4R70W

I seemingly have no life at the OD cancel button and it does not preclude OD while driving.

-Fuse 29 is good
-Pulled the entire shift lever and inspected all wires, and I mean the entire length of wires all the way up the lever itself.. Repaired two small areas of chafing. Verified continuity through all three wires.
-Tested the switch itself on the bench. It will provide continuity from the ground to the third terminal momentarily when depressed. I never could get it to illuminate when I applied power w my PP3, so I replaced today with original Ford part, no change though.
-At the plug under the dash I get +12V from a white/lime wire, ground from org/blu and the third wire (in the middle of the connector) is red/something which appears to be the trigger wire - I believe it gets grounded when the driver selects OD cancel based upon my testing of the button itself.

I never get any illumination of the "OFF" light ever - not in Run, not at start-up, not when the button is depressed by the driver in P or D.

I'm a bit lost now. I've got hot and ground to the button, button is new for good measure, all wires are good, fuse is good and has never blown in the short time I've had the vehicle, but it doesn't work.

Vehicle is a base model XL so I don't think it has auto headlamps. Not sure exactly what the seat belt minder is supposed to do, just illuminate the little red guy on the dash?

 

Sort of close....

Wire colors are vehicle harness, the switch assembly may be different.

RD/YE wire is HOT IN RUN/START via F29.

TAN/WHITE wire is pulled down to ground via a pull-down resistor in the PCM when the switch is not-activated. When the switch is activated, it connects that wire to power signalling the PCM that the operator has operated the switch.

The WHITE/Lt GREEN wire is connected to an open-collector driver in the PCM that, when the light is supposed to be turned on, is grounded by the PCM completing the circuit. If the PCM is not activating the lamp, that wire should read the same as the RD/YE wire.

You've probably done about all you can with a meter at the connector for the switch assembly. The only things left that are easy to do would be to inspect and re-seat the main harness connectors that those signals pass through. To do that, proceed as follows:

1. Disconnect battery negative terminal.
2. Disconnect connector C174 on the firewall. It's the top of three vertically stacked connectors near the brake vacuum booster. Look for any pushed or corroded pins, particularly pins 26 & 33 if you can make out the pin numbering.
3. Reconnect battery and retest to see if there was any affect. If none, disconnect the battery cable again and continue.
4. Disconnect the large PCM connector and likewise inspect it. The two pins of interest are pins 12 & 29.
5. Reconnect and retest.

There are some additional tests that can be made if the above doesn't resolve the issue but do those first. Further testing will require either a scan tool that can read the status of the switch and the commanded state of the TCIL or some comprehensive resistance checks that may require you to have an assistant (or some handy accessories for your meter).

 

Wow, fantastic tech, thank you! Re-seating the connector did it, although I can't say why - everything looked great. And thanks for the excellent description of what each wire should do.

 

Happy to help out, glad it worked out for you.