Case IH 7033 – Transmission Control Unit (TCU): Without differential lock pressure

The differential lock on these machines is an electro-hydraulically actuated wet multi-plate clutch. This code triggers when the system commands the differential lock to engage, but the differential lock pressure switch fails to detect the required hydraulic pressure to confirm that the engagement has actually occurred.

• Puma/Mid Range Magnum
• Puma 140
• Puma 155
• Puma 165
• Puma 170
• Puma 180
• Puma 185
• Puma 195
• Puma 210
• Puma 215
• Puma 225
• Puma 230
• Puma CVX
• Maxxum
• Magnum
• Steiger

1. 1

   Check the Differential Lock Pressure Switch to verify if it is functioning or stuck.

2. 2

   Inspect the Differential Lock Solenoid and test the solenoid valve responsible for directing hydraulic fluid to the diff lock clutch.

3. 3

   Inspect wiring and connectors for damaged wires, open circuits, or shorts to ground at the harnesses connecting to the solenoid and the pressure switch.

4. 4

   Check armrest switches to verify that the manual and auto differential lock switches in the armrest controller are communicating properly.

5. 5

   Perform a hydraulic pressure test on the low-pressure/lubrication circuit to verify that the tractor's hydraulic pump is producing adequate pressure and that the differential lock supply pipe is not leaking or blocked.

1. 1

   Preparation

   Park the tractor on a level surface, engage the parking brake, lower any implements, and turn off the engine. Relieve hydraulic pressure if required by your specific model's manual.

2. 2

   Locate the Components

   Locate the differential lock control valve block, which houses the solenoid and pressure switch (typically mounted on the transmission/rear axle housing).

3. 3

   Electrical Testing

   Disconnect the harness to the pressure switch and use a multimeter to test for continuity when the system is pressurized. Test the solenoid coil for proper resistance. If either fails, proceed to replacement.

4. 4

   Replace the Pressure Switch (if faulty)

   Unthread the old pressure switch from the valve body, install the new switch (ensuring the O-ring/seal is seated), and reconnect the electrical harness.

5. 5

   Replace the Solenoid (if faulty)

   Remove the retaining bracket/screws holding the solenoid to the valve body. Disconnect the electrical harness, pull the old solenoid, and swap in the new one. Always replace the associated O-rings on the hydraulic connector to prevent pressure leaks.

6. 6

   Reassembly & Testing

   Reconnect all hydraulic lines (such as the differential lock supply pipe) and electrical connectors. Start the tractor, clear the stored fault codes, and engage the differential lock (test both manual and auto modes) to verify that code 7033 does not return and the lock engages properly.