[rich951]

Hello all,
I have a 2013 LS 1.8 A and am having an issue with my rear brake lights and only the top third light coming on when pressing on the brake pedal, all rear running lights work expect when hitting the brakes as for the turn signals and hazards they work fine,I even tried messing around with the brake pedal switch and when I removed it the third light stopped working and when I re plugged it the top light continued to work again but still not the left or right light, the bulbs and fuses are good so I have no idea what it could be being that if it was the brake pedal switch that was bad I'm assuming the top would not work either. I would really appreciate any feedback or help on this.

Thanks

 

[ChevyGuy]

Looking at my manual, the left and right brake light have different fuses and run though different plugs. The brake position sensor feeds the BCM (Body Control Module) and it develops the signal for the 3 lights. The fact the high center light is coming on shows the BCM is getting the signal.

So, it looks like you probably have a bad BCM ($). However, I'd look to see if someone did a hack job of installing trailer wiring.

 

[Robby]

How have you determined the bulbs are good? The brake bulbs are dual filament.....one for running lights, one for brake lights.
Just because the running lights operate does not mean the bulbs are OK.....so, a couple of bulbs should be the first step.

As you discovered, the third brake lamp is a direct feed from the pedal switch, but, going further, that same signal is sent to the BCM and the brake light circuit is actuated by it.

If you replace the bulbs with no success then the BCM (and related circuits) will require some diagnostic time.

Rob

 

[anthonysmith93]

It's possible you have 3156 bulbs installed instead of 3157 as well. It will fit and light up for running purposes but won't illuminate brighter when braking because 3156 is single filament.

 

[rich951]

Robby,

I did remove the bulbs out and visually inspected them and noticed both filaments still in tacked but I guess I can spend a couple bucks on new bulbs and rule out the bulbs out, thanks for the suggestion.

 

[rich951]

i will look into the bulb number thanks for bring this to my attention.

 

[ChevyGuy]

As you discovered, the third brake lamp is a direct feed from the pedal switch, but, going further, that same signal is sent to the BCM and the brake light circuit is actuated by it.

According to my manual, the third light is controlled by the BCM. And it's a brake position sensor, not a switch. I'm pretty sure the BCM uses the position for other things besides the brake lights. Perhaps the brake assist.