Case IH 1077 - UCM – UCM / MTA CCM: Right external fender switch open circuit/short to GND

This fault code indicates an electrical failure in the circuit for the right-hand rear fender switch, which is typically used by the operator to control the Electronic Draft Control (EDC) rear hitch (raise/lower) or the rear PTO from outside the cab. The system has detected that the circuit is either broken (open circuit) or the signal wire is shorted directly to the ground. On some Magnum/Steiger models, code 1077 can also indicate 'Operator did not respond to EDC calibration procedure' if triggered during a hitch calibration sequence.

• VESTRUM CVX
• Magnum Series
• Puma Series
• Maxxum Series
• Farmall Series
• Steiger Series

1. 1

   Inspect the right rear fender switch for physical damage, cracked rubber boots, or water ingress (a common cause of shorts in external switches).

2. 2

   Trace the wiring harness from the right fender switch back to the cab interconnect/UCM. Look for pinched wires, chafing against the fender frame, or broken wires (open circuit).

3. 3

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

4. 4

   Using a multimeter, check the switch's signal wire for continuity to ground (which would confirm a short to GND). Check for reference voltage at the connector with the key ON.

5. 5

   Test the switch itself with a multimeter to ensure it shows continuity only when the button is actively pressed.

1. 1

   Power Down

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

2. 2

   Access the Switch

   Locate the faulty switch on the right rear fender. Depending on the model, you may need to remove a protective plastic cover or reach up under the fender lip.

3. 3

   Disconnect

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

4. 4

   Remove the Switch

   Depress the retaining tabs on the sides of the switch body or remove the retaining nut, and push the switch out through the top of the fender housing.

5. 5

   Harness Repair (If Applicable)

   If the diagnostic checks revealed a chafed wire shorting against the fender, repair the wire using weather-sealed heat shrink connectors and re-loom the harness.

6. 6

   Install New Switch

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

7. 7

   Reconnect

   Plug the electrical harness back into the switch. Ensure the weather seal on the connector is intact.

8. 8

   Test

   Reconnect the battery, turn the key ON, and clear the stored fault codes from the UCM. Test the fender switch to ensure the hitch/PTO operates correctly and the code does not return.