Case IH 520598-03 - BCM – BCM: High power voltage supply c - out of range - high

The control module is detecting that the voltage entering its "C" power supply circuit is exceeding the maximum allowable threshold. In a standard 12V system, this typically means the module is seeing voltage spikes (often >15V-16V), which usually points to an overcharging alternator, a short to a higher voltage source, or an internal module failure misreading the incoming voltage.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (Magnum 180, 200, 220, 240, 250, 280, 310, 340, 380, and 400)
• Case IH Steiger AFS Connect Series

1. 1

   Alternator Output Test: Start the engine and use a multimeter to measure the voltage across the battery terminals. If the voltage exceeds 14.5V - 15V, the alternator's voltage regulator has failed and is overcharging the system.

2. 2

   Battery Isolator & Relay Check: Check the battery isolator terminals and the BCM power distribution fuses for bridging or shorts.

3. 3

   Harness Inspection: Inspect the wiring harness that supplies power to the BCM (specifically the 'C' circuit power pins). Look for wire chafing where the power wire might be shorting against another high-current line.

4. 4

   Ground Verification: Check the main cab and BCM ground straps. A floating or poor ground can cause the module's internal voltage sensing to read artificially high.

5. 5

   Clear and Retest: Clear the fault code using the AFS Pro display or Electronic Service Tool (EST). If the code returns immediately with the key ON (engine off), suspect a wiring short or a failed BCM. If it only returns when the engine is running, suspect the alternator.

1. 1

   Disconnect Power

   Turn off the tractor, turn off the master battery disconnect switch, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the BCM

   Locate the Body Control Module inside the cab's electrical compartment.

3. 3

   Inspect Connectors

   Unplug the BCM connectors. Inspect the pins for corrosion, pushed-back pins, or moisture ingress, which can cause voltage bridging. Clean with contact cleaner if necessary.

4. 4

   Test Circuit "C"

   With the battery reconnected and the key in the ON position, probe the specific power supply "C" pin on the harness side. If the voltage is normal (approx. 12.6V): The wiring is fine, and the BCM has an internal hardware failure. The BCM must be replaced. If the voltage is abnormally high: Trace the circuit back to the fuse panel to locate the short.

5. 5

   Replace Alternator (If Applicable)

   If step 1 of the diagnostics revealed an overcharging alternator, replace the alternator assembly, clear the codes, and verify the BCM voltage returns to normal.

6. 6

   Replace and Program BCM (If Applicable)

   If the BCM is deemed faulty, install the new module. Note: A new BCM is not plug-and-play. You must connect the Case IH Electronic Service Tool (EST) to flash the module with the correct software payload for your specific tractor's PIN.