P0751 GMC - 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
- Low transmission fluid level
- Dirty transmission fluid
- Faulty 1-2 Shift Solenoid valve
- 1-2 Shift Solenoid valve harness or connectors
- 1-2 Shift Solenoid valve circuit is open or shorted
When the 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 recommend changing the transmission fluid and if possible removing 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.
When is the code detected?
The P0751 code is detected when the gear required by the ECM does not match the actual gear when vehicle is driven.
- Engine Light ON (or Service Engine Soon Warning Light)
- Transmission will not shift gears.
P0751 Gmc Description
The 1-2 Shift Solenoid (SS) valve controls the fluid flow acting on the 1-2 and 3-4 shift valves. The 1-2 SS valve is a normally-open exhaust valve that is used with the 2-3 SS valve, in order to allow four different shifting combinations.