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.
When a transmission solenoid is stuck off, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommended to change the transmission fluid and if possible, remove the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure, and that the transmission will need to be rebuilt or replaced.
The cost to diagnose the P0751 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 1 is part of the control solenoid valve assembly which has no serviceable parts. The control solenoid valve assembly is attached to the lower control valve body. The solenoid operates by the Transmission Control Module opening or closing the ground circuit. With the solenoid circuit grounded (solenoid on), the internal plunger and metering ball block the exhaust fluid creating signal fluid pressure. The signal fluid acts against the clutch select valve 2 to overcome the valve spring force moving it to the apply position, allowing the shift. The shift solenoid 1 is commanded ON in Park, Reverse, Neutral, and Drive 1 Engine Braking, and commanded OFF in Drive 1–6 gear ranges. The Diagnostic Trouble Code (DTC) will be set when the gear slip is greater than 400 RPM for 2 s.
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