P1777 GMC Ignition Retard Request Circuit Fault
Possible causes
– Step Motor harness is open or shorted
– Step Motor poor electrical connection
– Faulty Step Motor
– Step Motor poor electrical connection
– Faulty Step Motor
P1777 GMC Description
The step motor changes the step with turning 4 coils ON/OFF according to the signal from Transmission Control Module (TCM). As a result, the flow of line pressure to primary pulley is changed and pulley ratio is controlled
GMC Vehicle:GMC Acadia,GMC Canyon,GMC Envoy,GMC Savana 1500,GMC Savana 2500,GMC Savana 3500,GMC Sierra 1500,GMC Sierra 2500 HD,GMC Sierra 3500 HD,GMC Terrain,GMC Yukon,GMC Yukon XL 1500,GMC Yukon XL 2500,