Brake switch and total shutdown! Why?
Thread Starter
Senior Member
Joined: Jul 2015
Posts: 10,934
Likes: 2,457
From: Minneapolis
Brake switch and total shutdown! Why?
TL: DR...What do no brake lights, engine dying on the freeway, possibly weak battery and weird behavior all over all have in common? Skip to the end....
You like stories? It's been an interesting 24 hours. I have an evening delivery job, and a few stops into my run last night my brake switch appeared to die. No warnings, no DTCs (before or after it died), just no brake lights. Which also means no shifting out of Park. And in a pretty crappy area of town, I might add.
So, I played with fuses, there's one in each box that could be related. Looked fine, swapped them around anyway. Played with wires, reset computers via unhooking battery. No help. Found a nearby Autozone, $30 for a Duralast switch....nothing. Put the Ford switch back in and it worked!! Whew, now I can go home! (had already given up on the work route)
Until I'm about 1/4 of the way home and I started realizing some things weren't right. The HVAC was not blowing at all. And it seemed the cooling fans were also not on. Just as I'm contemplating these symptoms, the engine shut off at on the freeway in a towaway zone. Not even the hazards would work, just the radio and a message saying Shift To Park. Coast to the non-existent shoulder and am dead in a particularly bad spot in the dark. Didn't want to play with too much since my tires were about 4" from the white line and people speeding by. But, I tried resetting again, nothing. Got a cop to come sit behind me while I waited for a tow, so that was a little safer. After most of an hour of waiting I realize that systems have come back on. The hazards now work, etc. Still just waited for the tow at that point, but we were able to drive it up on the bed and back off again at home. So, WTF?!
Today, testing. Battery tested maybe a little weak, but starter and alternator test good. Forscan finds many codes from the shut down last night, but all communication errors. Clear them, nothing comes back. Huh. Truck runs, shifts, brake lights work. Ran some errands to give it a few starts, stops. All fine. Ok, tell my boss I'm back to work tonight. Sitting in the parking lot before leaving with my run, brake switch out again. [insert expletives] Boss takes my run for tonight. Play around with switch, try the Duralast some more, reset computers again. Check grounds all over, including at brake lights. Check bulbs. Run the one test I can without a multimeter (why didn't I toss that in the truck last night?), and that test suggests it isn't the switch. Start looking at wiring some more, can't find any damage.
19yo daughter is with me the whole time, btw. She's learning to be an HVAC tech, so getting her to help with some of all this. Finally I have one more thought. I find where the signal wire (VT/WH) goes, which is to the BCM. She checks the connector, big one with the lever-close action....it falls out in her fingers. [insert expletives] Check it for green crusties, just in case. Plug it in.
Sigh. Truck seems to be ok, now.
You like stories? It's been an interesting 24 hours. I have an evening delivery job, and a few stops into my run last night my brake switch appeared to die. No warnings, no DTCs (before or after it died), just no brake lights. Which also means no shifting out of Park. And in a pretty crappy area of town, I might add.
So, I played with fuses, there's one in each box that could be related. Looked fine, swapped them around anyway. Played with wires, reset computers via unhooking battery. No help. Found a nearby Autozone, $30 for a Duralast switch....nothing. Put the Ford switch back in and it worked!! Whew, now I can go home! (had already given up on the work route)
Until I'm about 1/4 of the way home and I started realizing some things weren't right. The HVAC was not blowing at all. And it seemed the cooling fans were also not on. Just as I'm contemplating these symptoms, the engine shut off at on the freeway in a towaway zone. Not even the hazards would work, just the radio and a message saying Shift To Park. Coast to the non-existent shoulder and am dead in a particularly bad spot in the dark. Didn't want to play with too much since my tires were about 4" from the white line and people speeding by. But, I tried resetting again, nothing. Got a cop to come sit behind me while I waited for a tow, so that was a little safer. After most of an hour of waiting I realize that systems have come back on. The hazards now work, etc. Still just waited for the tow at that point, but we were able to drive it up on the bed and back off again at home. So, WTF?!
Today, testing. Battery tested maybe a little weak, but starter and alternator test good. Forscan finds many codes from the shut down last night, but all communication errors. Clear them, nothing comes back. Huh. Truck runs, shifts, brake lights work. Ran some errands to give it a few starts, stops. All fine. Ok, tell my boss I'm back to work tonight. Sitting in the parking lot before leaving with my run, brake switch out again. [insert expletives] Boss takes my run for tonight. Play around with switch, try the Duralast some more, reset computers again. Check grounds all over, including at brake lights. Check bulbs. Run the one test I can without a multimeter (why didn't I toss that in the truck last night?), and that test suggests it isn't the switch. Start looking at wiring some more, can't find any damage.
19yo daughter is with me the whole time, btw. She's learning to be an HVAC tech, so getting her to help with some of all this. Finally I have one more thought. I find where the signal wire (VT/WH) goes, which is to the BCM. She checks the connector, big one with the lever-close action....it falls out in her fingers. [insert expletives] Check it for green crusties, just in case. Plug it in.
Sigh. Truck seems to be ok, now.