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 P0979 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 Transmission Control Module (TCM) high side driver 1 supplies 12 V to pressure control solenoid valve 3. The TCM also provides a control circuit and uses a low-side driver to control shift solenoid valve 3. The Diagnostic Trouble Code (DTC) will be set when the Transmission Control Module detects an open or a short to ground on the shift solenoid valve 3 control circuit for greater than 1 s.
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