If the Passat shift lock solenoid shorts to positive, you need to check the two wires of the solenoid—one power wire and one control wire—to see if there are any issues. If the wiring tests normal, the shift solenoid needs to be replaced. The left end of the shift valve is connected to the shift solenoid via an oil passage. When the solenoid is closed, there is no oil pressure acting on the left end of the shift valve, and the shift valve moves to the left under the force of the spring on the right end. When the solenoid is open, the main oil pressure acts on the left end of the shift valve through the solenoid, causing the shift valve to overcome the spring force and move to the right, thereby changing the oil passage and achieving the shift. The working principle of the car shift solenoid: 1. Car Solenoid Valve: Principle: When energized, the electromagnetic coil generates a magnetic force that lifts the closing member from the valve seat, opening the valve. When de-energized, the magnetic force disappears, and the spring presses the closing member against the valve seat, closing the valve. 2. Distributed Direct-Acting Solenoid Valve: Principle: It combines direct-acting and pilot principles. When there is no pressure difference between the inlet and outlet, energizing the solenoid directly lifts the pilot valve and the main valve closing member in sequence, opening the valve. When the inlet and outlet reach the starting pressure difference, energizing the solenoid first activates the pilot valve, increasing the pressure in the lower chamber of the main valve and decreasing the pressure in the upper chamber, thus using the pressure difference to push the main valve open. When de-energized, the pilot valve uses spring force or medium pressure to push the closing member downward, closing the valve. 3. Direct-Acting Solenoid Valve: Principle: When energized, the electromagnetic coil generates a magnetic force that lifts the closing member from the valve seat, opening the valve. When de-energized, the magnetic force disappears, and the spring presses the closing member against the valve seat, closing the valve. 4. Distributed Direct-Acting Solenoid Valve: Principle: It combines direct-acting and pilot principles. When there is no pressure difference between the inlet and outlet, energizing the solenoid directly lifts the pilot valve and the main valve closing member in sequence, opening the valve. When the inlet and outlet reach the starting pressure difference, energizing the solenoid first activates the pilot valve, increasing the pressure in the lower chamber of the main valve and decreasing the pressure in the upper chamber, thus using the pressure difference to push the main valve open. When de-energized, the pilot valve uses spring force or medium pressure to push the closing member downward, closing the valve. 5. Pilot-Operated Solenoid Valve: Principle: When energized, the magnetic force opens the pilot hole, rapidly reducing the pressure in the upper chamber, creating a high-low pressure difference around the closing member. The fluid pressure pushes the closing member upward, opening the valve. When de-energized, the spring force closes the pilot hole, and the inlet pressure rapidly forms a low-high pressure difference around the closing member via the bypass hole, pushing the closing member downward and closing the valve. 6. Pilot-Operated Solenoid Valve: Principle: When energized, the magnetic force opens the pilot hole, rapidly reducing the pressure in the upper chamber, creating a high-low pressure difference around the closing member. The fluid pressure pushes the closing member upward, opening the valve. When de-energized, the spring force closes the pilot hole, and the inlet pressure rapidly forms a low-high pressure difference around the closing member via the bypass hole, pushing the closing member downward and closing the valve.
