Case IH 12066 - EPL – EPL (Electronic Park Lock): Trailer relay – open wire / load and output to 12V

The control module has detected an electrical fault on the circuit that commands the trailer brake relay. The underlying condition is either an open circuit (a broken wire or disconnected load) or a short circuit directly to the 12-volt power supply.

• VESTRUM CVX
• Case IH Puma Series (150, 165, 180, 195, 210, 225 CVX)
• Case IH Maxxum Series (125, 150)

1. 1

   Verify the Code: Enter the ADIC display diagnostic menu, navigate to the EPL (XA) sub-menu, and use the HB menu to display stored fault codes and confirm 12066 is active.

2. 2

   Visual Inspection: Locate the trailer brake relay in the tractor's power distribution unit/fuse panel. Inspect the relay and its socket for corrosion, pushed-out pins, or signs of melting.

3. 3

   Relay Test: Remove the trailer brake relay and test the internal coil with a multimeter to ensure it is not open.

4. 4

   Circuit Testing (Open Circuit): With the battery disconnected, use a multimeter to check for continuity on the control wire running from the EPL controller harness to the trailer brake relay socket. A lack of continuity confirms an open wire.

5. 5

   Circuit Testing (Short to Power): Reconnect the battery and turn the key ON (engine off). With the relay uncommanded, test the control circuit for voltage. If 12V is present when it shouldn't be, the wire is shorted to the power supply (Vbatt).

1. 1

   Disconnect the tractor's battery to prevent electrical arcing or further module damage.

   Disconnect the tractor's battery to prevent electrical arcing or further module damage.

2. 2

   If the diagnostic tests proved the relay coil is open or internally shorted, discard the old relay and install a new OEM trailer brake relay into the power distribution unit.

   If the diagnostic tests proved the relay coil is open or internally shorted, discard the old relay and install a new OEM trailer brake relay into the power distribution unit.

3. 3

   If the wiring harness failed the continuity or voltage tests, trace the specific trailer brake relay control wire from the EPL module to the relay block.

   If the wiring harness failed the continuity or voltage tests, trace the specific trailer brake relay control wire from the EPL module to the relay block.

4. 4

   Repair any broken or chafed sections of the wire using proper automotive electrical splices and heat shrink. If the harness is severely melted or damaged, replace that section of the harness.

   Repair any broken or chafed sections of the wire using proper automotive electrical splices and heat shrink. If the harness is severely melted or damaged, replace that section of the harness.

5. 5

   Reconnect the battery and turn the ignition ON.

   Reconnect the battery and turn the ignition ON.

6. 6

   Enter the ADIC diagnostic menu, navigate to the EPL (XA) sub-menu, and access the H8 menu to clear the stored calibration information (EEPROM) and erase the fault code.

   Enter the ADIC diagnostic menu, navigate to the EPL (XA) sub-menu, and access the H8 menu to clear the stored calibration information (EEPROM) and erase the fault code.

7. 7

   Cycle the key and test the trailer brake system to ensure the relay engages properly and the code does not return.

   Cycle the key and test the trailer brake system to ensure the relay engages properly and the code does not return.