Case IH 12691 – ABS (Anti-lock Braking System) Module or Pneumatic Trailer Brake Control Module: Pneumatic output - delivery port - rear left - uncontrollable (if load/exhaust valves are activated for more than 4Hz, DTC is set)

The control module is unable to regulate the air pressure at the rear left pneumatic delivery port. The system sets this DTC when it detects that the load/exhaust valves are cycling too rapidly (more than 4Hz) in an attempt to achieve the target pressure. This is typically caused by a massive air leak, a mechanically stuck pneumatic valve, or a failed pressure sensor falsely reporting zero pressure.

• Puma
• Magnum
• Maxxum
• Optum

1. 1

   Perform an air leak test by letting the system build full pressure and listening or using soapy water near the rear left pneumatic delivery port.

2. 2

   Inspect the electrical harness and connectors to the rear left ABS modulator valve for corroded pins, moisture, or chafed wires.

3. 3

   Use the Case IH Electronic Service Tool (EST) to monitor live data for the rear left delivery port pressure sensor (a 0 PSI reading while pressurized indicates a failed sensor or wiring).

4. 4

   Check the pneumatic valve assembly for internal contamination from oil or water that could cause internal spools to stick.

1. 1

   Depressurize the System

   Safely park the machine on level ground, chock the wheels, and completely drain the air reservoirs to deplete all pneumatic pressure from the system.

2. 2

   Locate the Valve

   Locate the rear left pneumatic delivery valve / ABS modulator valve assembly (typically mounted near the rear axle or trailer brake coupling area).

3. 3

   Disconnect Electricals

   Carefully unplug the electrical connectors from the valve solenoids and pressure sensors.

4. 4

   Disconnect Air Lines

   Mark the air lines for proper reinstallation, then disconnect them from the valve assembly.

5. 5

   Remove the Valve

   Remove the mounting bolts securing the valve bracket to the chassis and extract the faulty valve.

6. 6

   Install the New Valve

   Mount the replacement pneumatic valve assembly and torque the mounting bolts to OEM specifications.

7. 7

   Reconnect Lines and Harness

   Reconnect the air lines (ensuring fittings are tight and sealed) and plug in the electrical connectors.

8. 8

   Test for Leaks

   Start the tractor, allow the air compressor to build system pressure, and spray soapy water on all disturbed fittings to ensure there are no leaks.

9. 9

   Clear Codes and Test

   Connect the Case IH EST, clear the 12691 fault code, and actuate the trailer brakes to ensure the load/exhaust valves operate normally without setting a new code.