Vpw gm class 2 stop lamp message

[04colyZQ8]

Looking for the message for stop lamp can’t seem to find it.

[antus]

Are you sure there is one and its not analog wired to the bulb?

[04colyZQ8]

Well the only inputs are to the pcm, tcm and abs module, but the bcm seems to receive it to supply voltage to the prnd321 lock solenoid. Key on can’t move shifter until you press the brake.

If I could get the scanner to read the bpp status on the bench could maybe find it.

I don’t understand in the truck tech 2, observation of bpp shoes applied , released.

On the bench it shows applied all the time! When I touch the brake Input wire to my abs and pcm to 12 volts nothing happens? I’m positive I have the correct pins, maybe I need to wire a load in like a resister or 1357 bulb. Then touch the wire to positive?

[ironduke]

90% sure you need to put some sort of a resistance load to gnd on that ckt. If you measure it you'll probably see some sort of reference voltage close to 12v.. It sees it as released when the voltage is brought near 0 volts when the brake lamps are not powered and are instead providing a path to ground thru the filaments..

[04colyZQ8]

Yes that did it I just used a relay as a load since I didn’t have a bulb and that worked