Sorry that's not correct. Pin 4 on connector J2 of the ECM is marked as a dedicated solenoid return for wire H807 Yellow. That is the how the return for the circuits for those three solenoids is completed, and what the ECM checks for (in addition to the power side of the circuit) when setting Diagnostic Codes. It has nothing to do with grounding to the machine frame.
Try this.
1. Locate CONN 1 & CONN 2 on the machine and disconnect both of them. (You do not have to worry about CONN 12 just yet because it connects to an accessory you do not have).
2. Disconnect connector J2 at the ECM.
3. Disconnect the 2-pin connectors at all three solenoids.
4. Check for continuity as follows. All wires will be Yellow: -
a) Wire H807-P19 between the Implement shutoff solenoid and Pin 33 on the half of CONN 2 that contains the male pins.
b) Wire H807-C33 between Pin 33 on the female (socket) half of CONN 2 and Pin 4 of ECM connector J2.
c) Wire H807-E12 between the Park Brake solenoid and Pin 38 on the male half of CONN 1.
d) Wire H807-C34 between Pin 38 on the female (socket) half of CONN 1 and Pin 4 of ECM connector J2.
e) Wire H807-E56 between the 2-Speed solenoid and Pin 36 on the male half of CONN 1.
f) Wire H807-C33 between Pin 36 on the female (socket) side of CONN 1 and Pin 4 of ECM connector J2.
Report your results.