Case IH 12523 – ABS ECU / Vehicle Control Module (VCM) / Cab Controller: Left or Right or Front AoH stroke too long during normal braking.

The piston or diaphragm inside the AoH converter is traveling further than its normal operating range (stroke) when the operator applies the brakes. This excessive travel triggers an 'End of Stroke Switch' mounted on the converter, typically caused by a loss of hydraulic pressure from air in the lines, low fluid, worn brake pads/discs, or internal seal failure.

• Puma 200
• Puma 215
• Puma 230 CVX
• Magnum 210
• Magnum 255
• Magnum 285
• Magnum 310
• Steiger series

1. 1

   Check hydraulic brake fluid reservoirs for the AoH system; a low reservoir strongly indicates a leak or severely worn brake friction material.

2. 2

   Visually inspect hydraulic lines from the AoH converter to the wheel hubs/calipers for weeping fluid, wet spots, or damaged hoses.

3. 3

   Inspect brake pad and disc thickness to ensure they are not worn beyond the manufacturer's service limit.

4. 4

   Verify the End of Stroke Switch on the affected AoH converter (Front, Left Rear, or Right Rear) is intact, wiring is undamaged, and it is not shorting out.

5. 5

   Perform a pedal feel test; a spongy brake pedal indicates air is trapped in the hydraulic circuit.

1. 1

   Bleed the Brakes

   If the fluid level is fine and no leaks are found, connect a bleed bottle to the brake calipers, pump the brakes, and open the bleeder valves to purge any trapped air.

2. 2

   Top Up Fluid

   Ensure the reservoir is filled with the correct OEM-specified fluid (often a specific mineral oil like Case IH Akcela LHM or equivalent—never use standard DOT brake fluid if mineral oil is specified).

3. 3

   Replace Worn/Leaking Components

   If a leak is found at a wheel cylinder or caliper, rebuild or replace the caliper and replace any damaged hydraulic lines. If the brake pads are worn out, install new pads and push the caliper pistons back into their bores.

4. 4

   AoH Converter Replacement

   If the system is fully bled, has no external leaks, and the brakes are in good condition but the stroke is still too long, the AoH converter likely has an internal seal failure. Safely relieve all air pressure from the pneumatic system, disconnect the air and hydraulic lines, and unbolt the AoH converter to replace it.

5. 5

   System Reset

   After repairs, perform a final brake bleed. Turn the tractor on, allow the air compressor to build full pneumatic pressure, and apply the service brakes to ensure the 12523 code does not return.