Case IH 12529 – ABS (Anti-lock Braking System) / EBM (Electronic Brake Module): Left AoH hydraulic pressure greater than 0.6 bar while not braking

The system detects a residual hydraulic pressure of more than 0.6 bar in the left brake circuit even though the operator is not pressing the brake pedal. This indicates either a false reading from a faulty pressure sensor or actual trapped hydraulic pressure causing the left brake to drag.

• Case IH Puma
• Case IH Optum
• Case IH Magnum

1. 1

   Verify actual pressure by connecting a mechanical hydraulic pressure gauge to the left AoH test port and comparing it to the electronic reading.

2. 2

   Inspect the left brake pedal linkage to ensure it is returning fully to its resting position and that return springs are not broken or obstructed.

3. 3

   Inspect the wiring harness and connector at the left AoH pressure sensor for corrosion, moisture, shorts, or open circuits.

4. 4

   Test the pressure sensor: if the mechanical gauge reads 0 bar but the diagnostic tool shows >0.6 bar, the sensor has failed internally.

5. 5

   Inspect the trailer brake control valve (AoH valve) for sticking or failing to return fluid to the sump if the mechanical gauge confirms actual residual pressure.

1. 1

   Secure the tractor

   Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Relieve hydraulic pressure

   Safely relieve all hydraulic pressure from the system by pumping the brake pedals several times until they feel firm.

3. 3

   Replace the sensor (if applicable)

   If replacing the sensor: Locate the left AoH pressure sensor on the brake valve block. Disconnect the electrical harness, unscrew the faulty sensor, and install the new one. Torque to OEM specifications.

4. 4

   Repair or replace the valve (if applicable)

   If repairing the valve: If the diagnostic checks proved the valve is sticking, remove the AoH trailer brake control valve assembly. Inspect the internal spools and springs. Rebuild the valve using an OEM seal kit or replace the entire valve assembly if the bore is scored.

5. 5

   Reconnect hydraulic lines

   Reconnect all hydraulic lines.

6. 6

   Bleed the brake circuit

   Bleed the left brake hydraulic circuit to ensure no trapped air is causing pressure anomalies.

7. 7

   Clear the fault code

   Turn the key to the ON position and use a diagnostic tool to clear fault code 12529 from the EBM/ABS module.

8. 8

   Test drive and verify

   Test drive the tractor and monitor the live data to verify that the left AoH pressure remains at 0 bar when the brakes are released.