Hi,

Wife's 2016 fiesta eco boost, both side brake lights not working, brake light above hatch back glass works ok.

Changed fuse, changed bulbs and side brake lights not working...

I believe that all three lights work off the same fuse, so is it likely that the brake switch above the brake pedal is faulty or is there anything else I should look at?

No signs of any corrosion on connectors.

Thanks in advance 

1 hour ago, Drooski said:

I believe that all three lights work off the same fuse, so is it likely that the brake switch above the brake pedal is faulty or is there anything else I should look at?

The brake lights are controlled by the Body Control Module (BCM). On most Fords the centre brake light is on its own circuit from the BCM for safety reasons. In the event of a fault with a brake light circuit, then at least one circuit should still work.

In a case like yours with the outer two lamps off, first remove both of the bulbs at the same time. Then fit one new bulb in one side only. Fit nothing on the other side. Try the brake lights and see if the new bulb lights. Repeat the process for the other side.

Let me know the results and I can advise further if needs be.

10 hours ago, unofix said:

The brake lights are controlled by the Body Control Module (BCM). On most Fords the centre brake light is on its own circuit from the BCM for safety reasons. In the event of a fault with a brake light circuit, then at least one circuit should still work.

In a case like yours with the outer two lamps off, first remove both of the bulbs at the same time. Then fit one new bulb in one side only. Fit nothing on the other side. Try the brake lights and see if the new bulb lights. Repeat the process for the other side.

Let me know the results and I can advise further if needs be.

Hi Unofix,

Many thanks for your response, I'm just away to grab a coffee and do as you suggested. I changed out the bulbs last night one at a time but with the opposite bulb still in place, so I'll do as you say and see if your suggestion solves the issue and let you know.

Hopefully it does as the car has it's MOT in Tuesday!

Please do the test with a brand new bulb, not one of the ones you already have.

11 hours ago, unofix said:

The brake lights are controlled by the Body Control Module (BCM). On most Fords the centre brake light is on its own circuit from the BCM for safety reasons. In the event of a fault with a brake light circuit, then at least one circuit should still work.

In a case like yours with the outer two lamps off, first remove both of the bulbs at the same time. Then fit one new bulb in one side only. Fit nothing on the other side. Try the brake lights and see if the new bulb lights. Repeat the process for the other side.

Let me know the results and I can advise further if needs be.

Hi I tried what you suggested and still no brake lights working any other suggestions? Cheers 

Seems like a fault with the BCM.

You are going to need to use FORScan to see what DTC it shows for the brake light circuit.

Do you have any other electrical problems?

26 minutes ago, unofix said:

Please do the test with a brand new bulb, not one of the ones you already have.

Both brand new bulbs purchased yesterday, cheers

No other electrical issues, all other lights functioning as they should, cheers

10 minutes ago, unofix said:

Seems like a fault with the BCM.

When I owned my old Mercedes, I sprayed the SAM unit (their equivalent BCM) with an electrical cleaner. It did 'cure' the fault I was having - is it worth doing the same with a BCM?

No. You need to use Forscan.