Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the P0977 GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
The shift solenoid 2 is part of the control solenoid valve assembly which has no serviceable parts. The shift solenoid 2 is a normally closed ON/OFF solenoid and is controlled by the Transmission Control Module through a low side driver. When the shift solenoid 2 is energized, shift solenoid 2 fluid pressure is directed to the clutch select valve 3. Power to the shift solenoid 2 is supplied by the Transmission Control Module through a high-side driver. The high-side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high-side driver will reset. The Diagnostic Trouble Code (DTC) will be set when the Transmission Control Module detects an internal high voltage electrical malfunction of the shift solenoid 2 control circuit when the shift solenoid 2 is commanded ON for 2 seconds.
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