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Discussion Starter #1
Hey guys,

My 2016 Ti Hatchback is having an issue where the LED DRL's are staying on. It started with me not noticing while it was in my garage over the weekend and Monday morning the car was completely dead. I charged it, it started, and I noticed the lights staying on.

It's out of warranty, but I thought it was the BCM after some checking of fuses and what not, so I dropped it off at the dealer and just told them to fix it (since I can't program a BCM myself). They did swap the BCM and programmed it. The problem went away, but my car was still dead the next Monday after sitting in my garage all weekend.

I dropped it back off and here's what they told me, "We found a relay in the trunk fuse block that controls ignition and it was bad/staying on." I didn't think there was any ignition relay all the way back there, BUT it seemed to make sense and fix the issue.

Fast forward two weeks to today. I just noticed my LED DRL's are on and the car has been turned off since I parked at work three hours ago.

I don't think I want to drop any more money into the Ford Dealership right now, but I'm at a lose.
Does anyone have any ideas?
Is it possible the relay fried the old BCM and had already fried the new one before it was found?
I wouldn't think it'd be possible for it to supply more than 12V which shouldn't kill a BCM.

I'd appreciate any help of ideas!
 

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Discussion Starter #5
I believe those leds are controlled by the fuse box under the hood. Maybe there's a bad relay?
I actually found they're controlled by an internal relay in the BCM (Body Control Module). After pulling every relay under the hood, nothing happened.

The latest thing it is doing is interrupted communication with not only the BCM, but the FCM (Fuel Control Module) as well. This means the car will not turn off because the fuel and ignition systems are still operating.

My best guess with all of this are the following:
  1. A ground is floating, bad, or loose. This would take a control module's "zero reference" and shift it. Anything that should read 0-5V would now read a shifted value. Say the ground floated to ~1V, and the control modules would now read 1-6V and all other devices would operate strangely since they'd get a signal 1V higher than what it's meant to be.
  2. The terminating resistors at the end of the CAN circuit is loose, bad, or corroded. This is typically 60 Ohm or 120 Ohm and would shift voltages based on changing the resistance.
So I'm wondering if anyone knows of the common ground points for control modules on the car. I want to start there.
And also if anyone knows where the terminating resistors are in the CAN circuits.

Does anyone know how many CAN BUS networks are on this vehicle and if any of them tough the BCM and FCM?
 
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