Case IH 520548-14 - BCM – BCM: Key switch: crank - invalid input voltage

The control module is receiving a voltage signal from the ignition key switch's "crank" (start) circuit that falls outside of the expected normal operating range. This is typically caused by an internal failure in the ignition switch, a short circuit (to ground or battery voltage), or an open circuit in the wiring harness between the switch and the module.

• MAGNUM AFS Connect
• Magnum 380
• Magnum 400 AFS Connect
• Steiger AFS Connect
• Quadtrac AFS Connect

1. 1

   Inspect the ignition key switch and its electrical connector for physical damage, corrosion, or loose/backed-out pins.

2. 2

   Using a digital multimeter, test the ignition switch for proper continuity and voltage output. Check the specific pin for the 'crank' circuit while turning the key to the start position to see if the voltage drops out or spikes erratically.

3. 3

   Disconnect the harness from the ignition switch and the BCM. Test the crank signal wire for continuity, and check for a short to ground or a short to battery voltage (B+) along the harness routing.

4. 4

   Inspect the BCM connectors for moisture intrusion or corrosion, which can cause invalid voltage readings on input pins.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical shorts or accidental cranking during the repair.

2. 2

   Access the Switch

   Remove the necessary interior cab trim panels or armrest console covers to access the rear of the ignition key switch.

3. 3

   Disconnect Harness

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

4. 4

   Remove the Switch

   Unscrew the retaining nut or bezel on the front of the console that holds the ignition switch in place, and pull the switch out from the rear.

5. 5

   Install New Part

   Insert the new ignition switch into the console, secure it with the retaining nut, and plug in the electrical connector.

6. 6

   Repair Wiring (If Applicable)

   If your diagnostic checks revealed a short or open wire in the harness rather than a faulty switch, splice and repair the damaged section of the wire using OEM-approved heat-shrink connectors.

7. 7

   Test

   Reconnect the battery. Turn the key to the crank position to verify the engine starts. Check the diagnostic display to ensure fault code 520548-14 has moved to an inactive state or can be cleared.