I have a 2012 XLT 4x4, 49,000 miles and it has no backup lights, I have checked all fuses and swapped relays and still no lights. Some of the internet stuff say there is backup switch and I don't see one on the tranny, am I missing something? All wiring is stock, I find no splices under the dash, factory trailer hitch, under the tail lights, I'm stumped.

 

There isn't one. The shift lever position is reported to the PCM via sensor that is internal to the transmission. The PCM, in turn, when it receives the appropriate signal, then sends a network message to the BCM indicating that reverse has been selected. The BCM, then responds by activating the FET driver for the reversing lamps.

You really need to scan the PCM (to determine if the transmission is correctly reporting shift lever position) and the BCM to see if it is reporting any faults with the reversing lamp circuit. There aren't many shortcuts.

Does the trailer reversing lamp relay "click" when the shift lever is switched into and out of the reverse position? That will give you a starting point as to whether it's a wiring issue or a control issue.

 

Thanks for the reply I'll check that and see what I get. I may have to take it to Ford for the scan as I don't have a scan tool other the a programmer that reads CEL codes.

 

OBDII interface and Forscan....

 

Its in the leadframe. Bet its bad.

 

Maybe, maybe not. It could also be a BCM that has shut down the circuit due to a detected fault.

Until he does needed diagnostics, it's all guessing.

 

???? it's at Ford, wifes truck so we know it must be fixed. Leadframe? No idea what your talking about.

 

The leadframe is the internal part of the transmission that includes the harness, connectors, and in-board electronics, including the TR sensor (which tells the PCM what position the shift lever is in). IMHO, it would be odd for a leadframe failure to only mis-report reverse shift lever position. It would be expected to also have other noticeable effects if the TR sensor was faulty as other shift lever positions would be incorrectly reported to the PCM.

More likely, it's an issue in the BCM as already mentioned.

Proper hands-on diagnostic procedures should be used to pinpoint, guessing over the internet can only go so far. Good luck at the Ford dealer, let us know what they come up with.

 

I'm betting it's a connector/wire in the harness. Corroded or eaten by rodents.

 

Certainly possible.

Until more information is provided, guessing is all we can do.

 

Can only guess without putting hands/eyes on. What I can say is over the past 40+ years working on vehicles for a living I've seen more wiring/connector issues (a lot more) than module/sensor issues.

 

Yeah, I hear you. The complication starting with the 09 [edit: 2011 is correct year as pointed out below] models was the "Smart FET" driver for all the lights that, if a fault of sufficient severity is detected, will shut down the circuit until the repair is made AND the body control module is reset with a scan tool.

 

BCM wasn't adopted to the F 150 until 2011, previously it was GEM/SJB. They do probably share some strategies though.

 

Yeah, good catch. Forgot it was a couple of years into that generation for the change. Since the OP has a '12, the BCM situation is in play.

 

BCM was the issue, Ford says they reprogrammed which leads to the new question. What would cause the BCM to forget what it was supposed to do, the truck pure stock?