*Update* 97 Powerstroke trans problem (Attn: Jon)

Hi Guys,

Got a weird trans problem and it's related to the brake switch. I don't have Lock Up

So far the Snap-on scanner says the brake is "ON" and brake press "ON"

1. The truck has no brake pressure switch.
2. Has 8 volts going to the brake tail lights with the key on and no brake action applied. Gets 12v with brake pedal pressed.
3. Disconnect rear ABS module and no help. Check brake switch power with test light at ABS module connector and it's off without brake applied and on with brake applied.
4. Checked brake applied power at PCM pin and it off when the peddel is not applied and on when applied.
5. Removed Multi-Fuction switch and I will loose power to the rear brake tail lights but the scanned still says Brake "ON"
6. Unpluged the brake switch and No Joy
7. Unpluged the wire harness at the tail lights No Joy
8. Found Third Brake light bulb burnt out and socket slightly melted
9. Swapped out PCM with a known good one No Joy
10. Truck does not have Cruise control
11. I disconnected the connector to the RABS brake valve No Joy

Somehow the brake is getting powered up but not on all circuts. I can't figure out how or why the computer says the brakes are on when I've seen the testlight go "On and Off" at that circut of the PCM?

The brake lights will come on when the key is turned on but do not come on with the key off..

#@%&*($% Help Please

sounds like you have a melted dash harness pretty common around here

Fix all the brake lights, pcm uses resistance through them to tell if the brake is on or off, bad bulb or burnt socked will do it.

Crazy yes, but thats how it is.

Maybe bad electric trailer brake controller???

Thanks soo much for the help!

I removed the plug from the cab to chassis. This is the wire harness that goes to the tail lights, fuel tank, ABS valve.
So here we go.. Got the pin out from our Alldata. I used a multi meter to see which feed was crossed. I could not find one. I reconnected the socket at the rear of the chassis to lighting and checked again. No feed.

So I applied 12 volts to each circut of the brake lights and used the mulit meter on "Volts" to see what I can find. Again no X feed? WTF? Ok reinstalled the connector to the cab and rechecked to see if the Brake lights came on with the IGN key in the run pos again. No lights.. Humm Put the Snap-on scanner back on and the brake switck On & Off was working again?

I had pulled back some of the covering on the harness and didn't see any wires that were melted? Drove the truck for several miles and no problems?

The truck did have a ABS "Light on" as reported by our Trans guy. But that is nolonger a issue either?

Well I guess it's fixed sorta? At least I know where the problem exists if it comes back.

Thanks again for the support! Ya Rock!