Center high mount stop light is not working

Good morning,

Yes, it could be.

If you have normal brake lights to the rear, then the brake light switch is working correctly. It sends a signal to the BCM and then it goes to the center light.

Before assuming it is the BCM, you need to test for power coming out of the BCM. If there is power, then it could be wiring to the socket.

I would test it first before replacing an expensive part that will not fix it.

Roy

Thanks Roy. I will check at my earliest convenience. By the way, I was told that the BCM checks for resistance from the bulb and then sends 12 volts. If not is found, it will not send 12 volts and the BCM will need to be reset. Is this true?

No, it is not. It would do that if it controlled the ground.

No, the BCM does not have to be reset.

You need to check the voltages from the BCM to the socket.

Roy

Thanks again. I imagine that I should also confirm that the brake switch is sending the input signal as well? 12 volts?

For the record. I'm a licensed electrician, not an auto mechanic. Sorry for any confusion.

No worries.

No to the brake light switch. As I stated before, if the brake lights in the rear are working, the switch is working and sending a signal to the BCM. You can test it but it will be good.

You need to concentrate on the wiring from the BCM to the third light.

Roy

Very good, thanks again.

You are welcome.

Roy

Hey Roy, can you send me a picture of the diagram in PDF format? It's hard to view when enlarged.

Try this one.

Roy

Thanks, that's a bit better.

Good.

Roy

Hey Roy, can you tell me which color modular plug this wire is in? There are 7.

It is marked as X6 pin2. It is a light blue wire.

Roy

I do see some numbers on the plugs, but no x designations. I thought I could figure it out by process of elimination, but I don't see a light blue wire in any position 2.

The pin arrangements are the same on all the connectors. There needs to be a light blue wire on one of them.

Roy

Based on the picture you sent me, I believe I found x6, but pin 2 looks gray...

The wire at the light is light blue....?

I see a light blue wire. Use an ohmeter to see if is the wire to the third light socket.

Roy

There is a light blue wire on that plug, but it's definitely not position 2. And it has power now I just checked. Brake is not pressed.

That is not it.

X1 has a light blue wire close to that one.

X1, X4 and X6 have light blue wires.

Roy

What do you mean by "close to that one"? I do see other light blue wires, but not in position 2...

I don't have a diagram of the connectors for markings of the X. You will need to do an ohm check from the third light to the light blue wire. You may have to check the ones on the connectors that have light blue wires.

Roy

Okay.The saga continues.

Keep me updated.

Roy

Will do. Need more time.

Okay.

Roy

Hey Roy! Are you available?

Yes, I am here.

Roy

Hi again. So, I was wrong, that wire was actually just a little different shade of blue. The diagram is accurate. I found a damaged wire and repaired it. Now with everything back together, I still have no power at that terminal number 2 leaving the BCM.

Okay, if you found the wire from the BCM to the third light and repaired it and there is no power when the brake is applied, then the BCM is the issue.

Roy

Okay, isn't odd that the only thing not working is that light considering all it controls?

Yes, but that module controls about 100 things or more and if there was an issue with the wiring such as a ground on the power wire, it may have damaged the internal control circuit just for that section.

Roy

I was hoping you wouldn't say that! It was a direct short.

Now what?

You need to replace the BCM and have it programmed to your truck. This is a module that must be programmed.

Roy

Sounds expensive! I'll look into it. Thanks, Dan

Found the part at rock auto.

Roy

Thanks, but it's a 2500. Who does the programming? Dealership?

Any shop with a Tech 2 scan tool. It can be any private shop and they will be much cheaper.

A dealer will be more than double a private shop.

Roy