Case IH 785-07 - UCM – UCM: Electro-hydraulic backup operated with engine running

The auxiliary electro-hydraulic backup system, which is designed to provide emergency hydraulic pressure for steering and braking if the main engine-driven pump fails, has engaged while the engine is actively running.

• MAGNUM AFS Connect
• Steiger AFS Connect

1. 1

   Check primary hydraulic steering and brake pressure to verify if the main pump is failing

2. 2

   Scan the UCM for concurrent fault codes indicating low primary steering pressure or auxiliary steering sensor faults

3. 3

   Inspect auxiliary steering/brake pressure sensors and steering angle sensors for electrical drift, open circuits, or shorts to ground/positive

4. 4

   Test the auxiliary backup pump relay and auxiliary steering cutoff valve solenoids to ensure they are not mechanically stuck in the closed/active position

1. 1

   Connect the Electronic Service Tool (EST)

   Read the UCM to verify code 785-07 is active. Look for any primary hydraulic pressure codes that might indicate a mechanical failure of the main pump.

2. 2

   Perform Mechanical Pressure Test

   Use a mechanical gauge to measure the primary hydraulic system pressure. If pressure is low: The fault is mechanical. Diagnose and repair the primary engine-driven hydraulic pump or the steering priority valve. If pressure is normal: The fault is electrical. Proceed to step 3.

3. 3

   Test the Auxiliary Pressure Sensor

   If primary pressure is fine, the UCM is likely receiving a false 'low pressure' reading. Test the auxiliary steering pressure switch/sensor. Replace it if it is reading out of specification.

4. 4

   Inspect the Wiring Harness

   Check the wiring harness connecting the UCM to the auxiliary steering solenoids (left/right auxiliary steering solenoids and cutoff valve solenoids) for shorts to power that could be falsely triggering the backup system. Repair any chafed or damaged wires.

5. 5

   Replace the Relay

   If the sensors and wiring are intact, replace the auxiliary hydraulic pump relay, as the internal contacts may have welded shut.

6. 6

   Clear and Verify

   Clear the UCM fault codes using the EST. Start the engine and verify that the electro-hydraulic backup pump no longer operates continuously.