Case IH 1079 - UCM – UCM / Transmission Control Module / CCM: Right external fender switch unexpected value

The control module is receiving an electrical signal (voltage or resistance) from the right rear fender switch that falls outside of its calibrated or expected parameters. This switch is typically used by the operator to control the electronic draft control (rear 3-point hitch raise/lower) or the Power Take-Off (PTO) from outside the cab. An unexpected value usually points to internal switch failure, moisture intrusion, or a wiring harness issue (such as a short to ground or short to battery voltage).

• VESTRUM CVX
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 85C
• Farmall 95C
• Farmall 105C
• Farmall 115U
• Puma 130
• Puma 140
• Puma 145
• Puma 160
• Maxxum 110 EP through 140 EP
• Magnum MX210
• Magnum MX230
• CX Series
• MX Series
• MXM Series

1. 1

   Inspect the right external fender switch for physical damage, cracked rubber boots, or moisture ingress, which is highly common for exterior-mounted switches.

2. 2

   Inspect the wiring harness leading to the right fender switch for chafing, pinches, or breaks.

3. 3

   Disconnect the switch and inspect the connector pins for corrosion, dirt, or bent terminals.

4. 4

   Verify the 5V reference circuit and ground circuit at the switch connector to rule out a harness short to ground or short to Vbat (battery voltage).

1. 1

   Turn off the tractor, remove the ignition key, and disconnect the negative battery cable to prevent electrical shorts.

   Turn off the tractor, remove the ignition key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the right external fender switch on the rear right fender housing.

   Locate the right external fender switch on the rear right fender housing.

3. 3

   Reach behind the fender panel (or remove the protective mudguard cover if equipped) to access the switch wiring.

   Reach behind the fender panel (or remove the protective mudguard cover if equipped) to access the switch wiring.

4. 4

   Disconnect the electrical harness connector from the back of the switch.

   Disconnect the electrical harness connector from the back of the switch.

5. 5

   Remove the retaining clips (e.g., wiring clip) or squeeze the locking tabs securing the switch to the fender, and push the switch out of its mounting hole.

   Remove the retaining clips (e.g., wiring clip) or squeeze the locking tabs securing the switch to the fender, and push the switch out of its mounting hole.

6. 6

   Insert the new OEM replacement switch into the fender cutout until it clicks securely into place.

   Insert the new OEM replacement switch into the fender cutout until it clicks securely into place.

7. 7

   Reconnect the electrical harness connector, ensuring the weather seal is fully seated.

   Reconnect the electrical harness connector, ensuring the weather seal is fully seated.

8. 8

   Reconnect the battery, turn the key on, and clear the stored fault codes from the UCM/Transmission module.

   Reconnect the battery, turn the key on, and clear the stored fault codes from the UCM/Transmission module.

9. 9

   Test the external switch to confirm proper operation of the rear hitch or PTO.

   Test the external switch to confirm proper operation of the rear hitch or PTO.