Case IH 12024 – Electronic Park Lock (EPL) controller: Ignition Key – Key Hardware Vs CAN Signals Coherence Check

This fault indicates a consistency check failure (mismatch) between the hardwired ignition key signal and the CAN bus signal representing the ignition key state. The controller is receiving conflicting information about whether the ignition key is turned on or off, meaning either the physical wire signal dropped out while the CAN signal remained active, or vice versa.

• Puma/Mid Range Magnum
• MAXXUM T4E
• VESTRUM CVX
• Case IH Puma Series
• Case IH Magnum Series
• Case IH Steiger Series
• Case IH Maxxum Series

1. 1

   Verify the tractor's battery voltage (the EPL is highly sensitive to voltage drops; codes 12052 and 12053 often accompany this if voltage drops below 10V or spikes above 16V).

2. 2

   Enter the instrument cluster's H diagnostic menu (or use the CNH Electronic Service Tool) and navigate to the EPL controller (Module XA).

3. 3

   Run the H5 - Switch operation test to verify if the controller is registering the physical ignition switch turns.

4. 4

   Run the H9 - Voltmeter diagnostic to check the voltage supply to the EPL module and the ignition circuit.

5. 5

   Inspect the ignition switch connector and the main harness connector at the EPL module for loose pins, corrosion, or moisture.

1. 1

   Secure the Machine

   Park the tractor on a flat, open surface. Ensure the handbrake is released and the shuttle lever is in the park position. Turn the machine off.

2. 2

   Access the Ignition Switch

   Remove the steering column/dash cowling to expose the rear of the ignition key switch.

3. 3

   Test the Harness

   Disconnect the ignition switch. Using a multimeter, check for continuity on the hardwired signal line running from the switch to the EPL module. Check the CAN High and CAN Low lines for proper resistance (typically 60 ohms across the network).

4. 4

   Replace the Switch

   If the wiring harness tests good but the H5 switch test showed intermittent dropouts when wiggling the key, the internal contacts of the ignition switch are failing. Replace the ignition switch assembly.

5. 5

   Clear Codes

   Reassemble the dash. Turn the key to the ON position. Access the diagnostic menu and navigate to the EPL module's HB menu to clear stored fault codes.

6. 6

   Verify Repair

   Cycle the ignition key off, wait 10 seconds, and turn it back on. Ensure code 12024 does not return.