Case IH 597-03 - UCM – UCM: Top of brake switch right voltage high

The control module is receiving an abnormally high voltage signal (typically a short to battery/power) from the right-hand circuit of the upper brake switch assembly.

• MAGNUM AFS Connect
• Magnum 180 AFS Connect
• Magnum 200 AFS Connect
• Magnum 220 AFS Connect
• Magnum 240 AFS Connect
• Magnum 310 AFS Connect
• Magnum 340 AFS Connect
• Magnum 380 AFS Connect
• Magnum 400 AFS Connect

1. 1

   Visual Inspection: Locate the brake switch assembly inside the cab and inspect the wiring harness connecting the switch to the UCM for chafing, pinched wires, or melted insulation that could cause a short to a 12V power source.

2. 2

   Voltage Test: Disconnect the brake switch connector, turn the ignition ON, and use a multimeter to measure the voltage at the harness pins. High voltage on the signal return wire indicates the harness is shorted to power.

3. 3

   Switch Continuity Test: Test the brake switch itself for internal shorts. If the internal contacts are fused together or shorting to the power supply pin, the switch is faulty.

4. 4

   UCM Pin Check: Inspect the UCM connector pins for corrosion, water ingress, or bent pins that could be bridging a power circuit to the brake switch input circuit.

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

   Remove the necessary cab trim panels around the brake pedal assembly or the armrest console (if diagnosing the park brake switch) to gain clear access to the switch.

3. 3

   Disconnect and Remove

   Unplug the electrical connector from the faulty brake switch. Unbolt or unclip the switch from its mounting bracket.

4. 4

   Harness Repair (If Applicable)

   If the diagnostic checks revealed a short to power in the wiring harness, splice in a new section of wire or replace the damaged harness section (e.g., Wire Harness, Park Brake Switch) before installing a new switch.

5. 5

   Install New Part

   Mount the replacement brake switch into the bracket and adjust the physical clearance/throw if required by the mechanical pedal.

6. 6

   Reconnect

   Plug the electrical connector back into the switch. Reconnect the battery.

7. 7

   Clear Codes

   Turn the ignition on and use the AFS Connect display or an electronic service tool (EASy) to clear the 597-03 fault code. Test the brake pedal to ensure the code does not return and the brake lights/park brake function normally.