Case IH 9018 - UCM – UCM: External fender switch unexpected value

Triggers when the control module receives a voltage or signal from the external rear fender switch (used to operate the rear hitch or PTO from outside the cab) that falls outside the expected normal operating parameters. This "unexpected value" is typically caused by a stuck button, water/moisture ingress inside the switch, a short to ground/battery, or an open circuit in the wiring harness.

• MAXXUM T4E
• VESTRUM CVX
• Puma Series (140, 145, 165, 180, 195, 210, 225)
• Maxxum Series (110 EP, 115 EP, 120 EP, 125 EP, 130, 140)
• Farmall U Series (105U, 115U)
• Magnum & Steiger Series
• MX Series (MX80C through MX170)

1. 1

   Visual Inspection: Inspect the external fender switches (both left and right sides) for physical damage, cracked rubber boots, or buttons that are physically stuck in the depressed position.

2. 2

   Connector Check: Reach behind the fender and disconnect the wiring harness from the switch. Inspect the pins for green corrosion, rust, or moisture, which is highly common for exterior switches.

3. 3

   Wiring Harness Test: Using a multimeter, check the wiring harness from the fender switch back to the UCM for continuity. Verify there are no shorts to ground or shorts to battery voltage (Vbat).

4. 4

   Switch Continuity Test: Test the switch itself with a multimeter to ensure it only shows continuity when the raise/lower or PTO buttons are actively pressed.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent any short circuits while working on the UCM wiring.

2. 2

   Access the Switch

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

3. 3

   Disconnect Harness

   Unplug the wiring harness connector from the back of the switch.

4. 4

   Remove the Switch

   Depress the retaining clips (or remove the mounting screws, depending on the model year) securing the switch to the fender and push the switch out of its mounting hole.

5. 5

   Clean the Area

   Wipe away any dirt or debris from the fender opening to ensure the new switch seats properly.

6. 6

   Install New Part

   Snap the new replacement switch into the fender opening until the clips lock it into place.

7. 7

   Reconnect

   Apply a small amount of dielectric grease to the electrical connector to prevent future moisture ingress, then plug the wiring harness back into the switch.

8. 8

   Test

   Reconnect the battery, turn the ignition on, and clear the stored 9018 fault code. Test the external hitch raise/lower or PTO engagement to verify the repair.