I have a 2004 F150 Lariat. The reverse lights, cruise control and shift interlock are acting up.
I have checked the fuses, lamps and relays for the reverse lights but found no issue.
The shift interlock engages when the ignition is turned on and doesn't disengage... even when he brake switch is unplugged. The brake lights work just fine so I don't think its the problem. The shift interlock is functioning so I don't see the problem being there either.
The cruise control does nothing when the button is pressed. I think these issues are related.... somewhat. I understand that the switch on the driver side of the trans. monitors the position of the shifter. If this was not seeing that the trans was in reverse the lights wouldn't turn on. I replaced the sensor/switch on the transmission today and still no go. I am really at a loss here.
I searched the other forums but users either didn't post the solution or their trucks were fixed by the replacement of the trans switch.

Please help me!

 

So ive done more searching... I found a wire that pulled out of the connector at the rear of the truck. This was the reverse wire. I repaired the connection and now the rev. lights are working.
I searched for somewhere feedback was going back up the brake wires but I don't think this is the issue because the brake lights only come on with the brake pressed.

This does however group the no cruise and shift interlock as one issue. Again ive changed the switch on the trans and verified the brake switch. which by the way the interlock stays engaged even when the brake switch is unplugged.... its like its feeding off the ignition. I looked for sticking relays but found none.......help please.

 

Okay, so Im now pretty sure im looking for the brake shift interlock switch. Ive checked the in/out wires on the brake pedel. The out has 12v on it even when unplugged... I check another truck and it does not have 12v when unplugged... only when pluged in.

Question.. is there a switch under the gear selector? I know there is a solenoid on the driver side of it but I read somewhere there was a switch under It...

 

I haven't seen a switch underneath the gear selector--the solenoid is the only mechanical part I'm aware of concerning your issues--that, or a bad trans cable or shifter. Can usually find a shifter here, or eBay. My brother bought mine for my project for $25 on eBay.