Case IH 701-03 - UCM – UCM: Low voltage in the neutral switch of the transmission control lever

Low voltage in the neutral switch of the transmission control lever. If presenting as an auxiliary input voltage high error, it indicates the control module is receiving a voltage signal exceeding the maximum expected threshold (typically 4.5V to 5V), usually indicating a short to power in the wiring harness, a failed sensor, or an open ground circuit.

• MAGNUM AFS Connect
• Steiger
• Puma
• Optum

1. 1

   Verify the Code: Use the AFS Pro display or EST (Electronic Service Tool) to check if the code is 'Active' or 'Inactive'.

2. 2

   Inspect the Harness: Check the wiring harness between the UCM and the auxiliary input connection (or the transmission control lever, per the official 701-03 description) for chafing, pinched wires, or water ingress that could cause a short to power or an open ground.

3. 3

   Check UCM Supply Voltage: Verify that the UCM itself is receiving the correct operating voltage.

4. 4

   Test the Sensor/Switch: Disconnect the sensor or switch in question. If the code changes from 'Voltage High' to 'Voltage Low' (or vice versa), the wiring is likely intact, and the sensor/switch itself has failed internally.

1. 1

   Turn off the machine and disconnect the battery ground.

   Turn off the machine and disconnect the battery ground.

2. 2

   Disconnect the connector at the UCM and the connector at the affected switch/sensor.

   Disconnect the connector at the UCM and the connector at the affected switch/sensor.

3. 3

   Use a multimeter to perform a continuity test on the signal wire and ground wire.

   Use a multimeter to perform a continuity test on the signal wire and ground wire.

4. 4

   Repair or replace any damaged sections of the wiring harness.

   Repair or replace any damaged sections of the wiring harness.

5. 5

   If the harness tests good, replace the faulty switch/sensor.

   If the harness tests good, replace the faulty switch/sensor.

6. 6

   Reconnect all components, power on the machine, and use the AFS Pro monitor to clear the inactive fault codes.

   Reconnect all components, power on the machine, and use the AFS Pro monitor to clear the inactive fault codes.