Stall/no start unless parking brake engaged

2005 4.0L 6 speed

Installed a Banks pedal monster that a friend gave to me a few months ago.

Recently a P2121 code (throttle/pedal position, sensor/switch D circuit, range performance) was given. The truck would go into limp mode and would need to be restarted. I pulled the Banks (on the way back to them for a warranty) but the truck continued to intermittingly give the code/ and display the symptom.

The last few time I've driven it, it has stalled and would restart after a 20-30 second wait.

I had it in the shop for an inspection and the tech couldn't get it to start unless the parking brake was slightly engaged. They had no answers so I drove it home and it has randomly needed the parking brake engaged to start. Tonight the truck would not STAY running unless it was engaged but as I was driving it home, I tested taking it off and it would stay running but would not gain rpm's at all with throttle input. I was able to stall it by cycling the parking brake when I got home.

Currently no CEL but thinking about putting a throttle position switch in it to start.

Any ideas why the parking brake is affecting this condition?

Apologies for the long post and thank you in advance for your time and consideration!

 

Look where the parking brake linkage is under the dash for anywhere it could be rubbing on wiring.

 

Yes, going to check that.