Do I need to flash the BCM if I replace it?

I have a 2008 Mazda 6i and the horn, brake lights and cruise control do not work. The repair shop says the BCM shows signs of water damage and needs to be replaced. Pulling the old one is easy enough and I even found a replacement on Ebay.

Do I have to take it to a dealer and get it flashed?

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    Does the new one have exactly the same part no?
    – HandyHowie
    Dec 24 '15 at 7:16
  • I would take a look at fuses, wiring diagrams and wiring before jumping to the BCM. I would think the horn and brake lights would be able to function without the BCM. Maybe I just believe too much in KISS to understand why you would need a computer to run a switch and light/horn.
    – rpmerf
    Dec 24 '15 at 16:08
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    Checked and replaced fuses several times and they continue to blow so I know there is a wiring problem. I and the shop have looked for grounding and shorts as well as possible.
    – user13830
    Dec 24 '15 at 16:12

The BCM should not need to be reprogrammed after installation. If it does not work on power up then have it checked. It is connected to and operates many features of the car including the CAN network.

Check the old one for water damage. If it has been damaged; look at the hood release cable, these have known to bring water in to the area above the BCM and then drip water into it. A new cable is needed to repair this leak.

  • 1
    Thank you. That confirms what I've been told in another forum. I will verify the part number and check the hood release where it passes through the firewall.
    – user13830
    Dec 24 '15 at 12:42

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