i have a 2001 chevy 2500 HD 4x4 with the 8.1l and allison transmission. the "service engine soon" light came on my truck and my scanner read the code P1781. under the GM codes it says "engine torque signal circuit". does anyone know what that means or what i need to change out of my truck to fix it? i haven't noticed any power loss, i have been hauling cars all weekend. thanks.