So i noticed the third brake light on my wifes 05 malibu was not coming on when the brakes are applied. I removed the third brake light and noticed they use leds and not a regular bulb. Maybe a burned resistor? Checked to see if voltage was getting to the brake light and the volt meter showed voltage when the brakes are applied. Also noticed that the brake lights on the car don't come on when you step on the pedal unless the key is in the on position. Is this normal for the malibus? Never really paid attention to it since we bought it new back in 05 but my trucks lights come on as soon as you press the brake pedal. Any ideas? Can't find a reason why the third brake light would just stop working and since the brake light is sealed i don't want to break it apart.

leds go too. some times gm uses ground control though so just because you have 12v doesnt meen its definately the bulb, i would some jumper wires on a battery directly to the bulb plug and see if it works if not you know its in that.

Do you have the regular 4-door body style, or, do you have the Malibu Maxx?

Four door.

So if the leds work when connected to the battery then it would probably be the ecm out put to the brake light. What about the brake lights coming on only with the key on the on position is this also a Gm thing. Never noticed this when we got the car but my truck lights them just by stepping on the brake pedal.

The brake lights would still work even without the key having to be on, I'm not sure why you'd have to have the key on to begin with, IMO...

not necessarily the pcm some cars have a bcm or light control module that control all the lights

That'* what i thought. Gonna have to look into it. Maybe that'* what is causing the third brake light to not work.

Check to see if you have a fuse for the 3rd brake light. My 2000 Blazer has the LED 3rd brake light bar and it has its own fuse. Weird I know.

Well, hooked up the third brake light straight to battery.NOTHING. Left it unplugged and stepped on the brakes with no key in the ignition still the brake lights don't come on. Moved the the turn signal stalk out of auto and manually turned on the parking lights.Nothing. Put the key into the ignition to the on position and they came on stepped on the brakes and the brake lights came on. Still weird. Could the the third brake light be needed in good working order for all the lights to work correctly? Just about to give up. No big deal since they all work when the key is the on position or the car running.