Case IH 5145 – UCM (Universal Control Module): Aux Thumbwheel Axis Pin B Shorted To Power

The control module is receiving a voltage signal from Pin B of the auxiliary hydraulic control thumbwheel (a Hall Effect sensor located on the joystick) that is higher than the expected normal operating range. This indicates that the signal wire is short-circuited to a power source (such as a 12V battery line or a 5V reference line).

• skid steer
• Compact Track Loaders (CTL)
• SR series
• SV series
• TR series

1. 1

   Visually inspect the wiring harness running from the joystick down through the control pod for pinched, chafed, or bare wires rubbing against a power wire or the metal chassis.

2. 2

   Perform a disconnect test: Turn the machine off, disconnect the electrical connector at the base of the affected joystick, turn the key back on, and check active fault codes.

3. 3

   If the code changes to 5144 during the disconnect test, the short is located inside the joystick assembly or the thumbwheel switch itself.

4. 4

   If code 5145 remains active during the disconnect test, the short to power is located in the machine's main cab harness between the joystick connector and the UCM.

5. 5

   Use a digital multimeter to probe the joystick harness connector. Verify that the 5V reference and ground circuits are intact and that the signal wire for Pin B is not showing voltage when disconnected from the UCM.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical damage during repair.

2. 2

   Access the Harness

   Remove the protective rubber boot and access panels around the joystick base.

3. 3

   Harness Repair

   If the diagnostic disconnect test pointed to the main harness, locate the damaged section of the wire. Repair the shorted wire using proper soldering and heat-shrink tubing, or replace the affected harness section.

4. 4

   Switch/Joystick Replacement

   If the short is inside the joystick, attempt to replace just the thumbwheel switch by de-pinning the switch wires from the joystick harness block. If the thumbwheel is integrated into the handle grip and not serviced separately, replace the entire joystick handle assembly.

5. 5

   Reassembly and Testing

   Reconnect all harnesses, reinstall the joystick boot, and reconnect the battery. Turn the key on, clear the inactive fault codes via the instrument cluster, and test the auxiliary hydraulics for proper proportional operation.