Question

2006 GMC Sierra 2500 HD 8.1L with engine code P1779 and the engine will not start

Answer 1

P1779 Engine torque signal

This is a Type "B" code what it uses is the throttle and engine speed to calculate torque. By means of the crank sensor and TPS, If it does not start you need a CKP (crank position sensor). The location of the CKP is in the back of the transmission. If the crank sensor was failing the transmission will code P1779 and there you have erratic shifting.