Case IH 2438 – CCU: Voltage from R3 switch too high

The voltage signal coming from the Range 3 (R3) position switch on the transmission gear/range lever is exceeding the maximum expected threshold. This typically points to a short-to-power in the wiring harness, a disconnected/open circuit, or an internally shorted switch.

• Farmall
• Farmall 90C
• Farmall 100C
• Farmall 110C
• Farmall 120C

1. 1

   Visually inspect the R3 switch and its wiring pigtail for physical damage, chafing, or pinched wires that could cause a short to a 12V power source.

2. 2

   Disconnect the R3 switch and check the pins on both the switch and harness side for corrosion, moisture, or bent pins causing an open circuit.

3. 3

   Perform a voltage test with the key ON by probing the signal wire at the switch connector (a 12V+ reading instead of a 5V reference indicates a short to power).

4. 4

   Test the R3 switch continuity with a multimeter set to Ohms (should have continuity when shifted into Range 3, and infinite resistance/OL when shifted out).

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Access the Switch

   Remove the right-hand console trim or cab floor panels as necessary to access the base of the transmission range lever assembly.

3. 3

   Remove the Faulty Switch

   Disconnect the electrical connector from the R3 switch. Remove the retaining screws or unthread the switch from the transmission/lever housing.

4. 4

   Install the New Switch

   Install the replacement R3 switch. If it is a threaded sensor, ensure the O-ring is seated properly and torque to OEM specifications.

5. 5

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a short to power in the harness, trace the wire back to the CCU, locate the chafed section, and repair it using heat-shrink butt connectors or replace the affected harness section.

6. 6

   Reassembly & Clearing Codes

   Reconnect the switch, reassemble the cab console, and reconnect the battery. Turn the key ON and use the tractor's diagnostic menu (or an EST service tool) to clear the CCU fault codes.

7. 7

   Test Operation

   Shift the tractor through all ranges, specifically ensuring Range 3 engages smoothly without throwing the 2438 code.