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I have some weird electrical problems on my 2018 F250 with gas engine. My rear brake lights do not work. My radio can not be controlled from the radio controls, but does seem to work from steering wheel controls. My A/C controls do not work. Rear windows work, but not the front windows. Any ideas on where to start? Body control module??
In all cases of weirdo seemingly unrelated electrical issues you must check 2 things:
1. Low battery voltage, and by low I mean low by just a little bit. As you have a 2018 the OEM battery is probably at end of useful life.
2. Those now infamous connectors between the rear bumper and spare tire. They can collect moisture and corrosion. Blow them out, gently clean the pins and apply dielectric grease.
Those two steps fix nearly all such issues about 90% of the time.
The low battery gremlin almost got me. My daughter's 15 Mustang had what appeared to be a loose connection in the left turn signal. Almost started pulling stuff apart. Car would start fine. Replaced battery and haven't had a problem since.
It seems the electrical gizmos are more sensitive to low voltage than a starter.
Battery has 12.60 volts and load tested fine. Using forscan, I was able to see multiple BCM codes.U0199:87 U0256:87 U0200:87 U0142:87 B14AA:11. Anyone know where to get BCM wiring diagrams? Thanks in advance.
Good call Jim. After spending a little time on the battery and tracing down wires. We made it to the back connector and found this. Truck is now fixed and everything works. Apparently one or two of these wires provided a ground or power to the Body Control Module / Front Control Module, causing the radio and A/C issues. Thank you for your help.
My brother purchased this vehicle second hand. Apparently the previous owner replaced rear bumper with sensors to a bumper without sensors and installed a 5th wheel and spliced some of the wiring. When they sold it, they removed the 5th and wiring, taped / wrapped it up, and shoved it up over the spare tire. Everything worked when my brother picked it up and drove it home. When he removed the spare tire during a pre-trip inspection and service, he must have knocked something loose and just didn't think about it. OR it just didn't click that he did anything wrong.
