Case IH 2378 – Transmission Control Unit (TCU): Parking lock switch - Voltage too low

The control module is detecting a voltage signal from the parking lock switch circuit that is below the minimum expected threshold. This typically points to an open circuit, a short to ground in the wiring harness, or an internal failure of the switch itself.

• Puma/Mid Range Magnum
• Case IH Puma Series
• Case IH Maxxum Series
• Case IH Optum Series
• Case IH Farmall Series

1. 1

   Verify overall battery and charging system voltage to rule out false codes triggered by low system voltage

2. 2

   Inspect the wiring harness between the Electronic Park Lock (EPL) switch and the Transmission Control Unit for chafed wires, pinched lines, or shorts to ground

3. 3

   Disconnect the EPL switch and inspect connector pins for corrosion, moisture ingress, or pushed-out pins

4. 4

   Use a multimeter to verify the transmission controller is sending the correct reference voltage to the switch

5. 5

   Test the switch's internal continuity across its different states to check for internal failure

1. 1

   Safety First

   Park the tractor on a level surface, chock the wheels (since the electronic park lock is malfunctioning), and turn off the battery disconnect switch.

2. 2

   Locate the Switch

   Locate the Electronic Park Lock (EPL) switch. Depending on the cab configuration, this is typically integrated into the shuttle control lever (FNR lever) on the steering column or on the armrest console.

3. 3

   Access the Component

   Remove the necessary plastic trim panels or steering column cowlings to access the switch wiring.

4. 4

   Disconnect

   Unplug the electrical connector from the faulty EPL switch.

5. 5

   Remove and Replace

   Remove the mounting screws or retaining clips securing the switch. Install the new Parking Lock Switch and secure it in place.

6. 6

   Reconnect

   Reconnect the electrical connector, ensuring the locking tab clicks into place securely. Reinstall all trim panels.

7. 7

   Clear Codes

   Turn on the battery disconnect and the key switch. Clear the fault code using the tractor's diagnostic display (H menu) or the Case IH Electronic Service Tool (EST).

8. 8

   Test Operation

   Test the Electronic Park Lock by shifting the shuttle lever into the park position. You should hear the EPL actuator motor engage the parking brake. Verify that fault code 2378 does not return.