Case IH 4252 - UCM – UCM: Right external fender switch is active at key-on

When the tractor is powered up, the system runs a safety interlock check. If the controller detects that the right rear fender switch (which typically controls either the rear Power Take-Off (PTO) or the Electronic Draft Control (EDC) 3-point hitch) is in the "active" (pressed or closed-circuit) state during the ignition cycle, it throws this code. This is a safety mechanism designed to prevent the unexpected engagement of the PTO or sudden movement of the rear hitch when the tractor is started.

• MAXXUM T4E
• VESTRUM CVX
• Maxxum Series
• Puma Series
• Magnum Series
• Farmall U / C Series

1. 1

   Visually inspect the right rear fender switch for physical damage, packed dirt, mud, or ice that might be physically jamming the button in the depressed position.

2. 2

   Perform a disconnect test: turn the key off, disconnect the wiring harness from the back of the right fender switch, and turn the key back on. If the code changes to an 'open circuit' code or clears, the switch is internally shorted.

3. 3

   Inspect the wiring harness if the code remains active with the switch unplugged. Trace the wiring from the fender down to the UCM, looking for pinched wires, rubbed insulation, or a short to power (12V).

4. 4

   Perform a multimeter continuity test on the disconnected switch. It should only show continuity when the button is actively pressed. If it shows continuity while resting, it has failed internally.

1. 1

   Power Down

   Turn the ignition key to the OFF position and remove the key.

2. 2

   Clean the Area

   Thoroughly clean the area behind the right rear fender to prevent dirt from falling into the electrical connectors.

3. 3

   Access the Switch

   Reach under the fender lip or remove the switch bezel/housing (depending on the specific cab/fender package) to access the rear of the switch.

4. 4

   Disconnect

   Unplug the electrical connector from the switch.

5. 5

   Remove the Switch

   Remove the retaining nut, locking tabs, or switch clamp (e.g., clamp part # 220416A2) holding the switch in the fender housing. Pull the faulty switch out.

6. 6

   Install the New Part

   Seat the new switch into the fender cutout and secure it with the retaining hardware.

7. 7

   Reconnect

   Plug the electrical harness back into the switch. Ensure the weather-pack seal clicks into place to prevent moisture intrusion.

8. 8

   Verify Repair

   Turn the ignition key to the ON position. Verify that fault code 4252 has cleared from the dash/A-pillar display. Test the switch to ensure the hitch or PTO operates correctly.