Case IH 158-15 - VCM – VCM: Keyswitch Battery Potential - Data Valid But Above Normal Operating Range

The supply voltage to the controller is too high. The module is receiving a voltage input that exceeds the maximum safe operating threshold (typically indicating an overcharging alternator or an external high-voltage event like an improper jump-start).

• MAGNUM AFS Connect
• Patriot 2240
• Patriot 3230
• Patriot 3320
• Patriot 3330
• Patriot 4420
• Patriot 4430
• Magnum
• Puma
• Steiger

1. 1

   Measure alternator output voltage at the battery terminals with the engine running (if climbing above 15-16V, the alternator is overcharging)

2. 2

   Verify with the operator if the machine was recently jump-started (applying a 24V jump-start to a 12V system will trigger this code)

3. 3

   Measure voltage directly at the VCM power supply pins and the keyswitch input pin to verify if the high voltage is isolated to the VCM circuit or present system-wide

4. 4

   Inspect the wiring harness between the battery, keyswitch, main power relay, and the VCM for any shorts to a higher voltage source

1. 1

   Disconnect battery

   Turn off the machine and disconnect the negative battery cable to prevent further electrical damage.

2. 2

   Replace alternator assembly

   If the diagnostic checks revealed an overcharging alternator, remove the serpentine belt, disconnect the alternator electrical connections, and replace the alternator assembly.

3. 3

   Repair wiring harness

   If the alternator is functioning normally but the VCM power circuit is shorted to another power source, trace the wiring harness and repair the shorted wires using OEM-approved heat-shrink connectors.

4. 4

   Replace Vehicle Control Module

   If the machine was subjected to a severe overvoltage event (like a 24V jump-start) and the VCM is unresponsive or internally shorted, replace the Vehicle Control Module.

5. 5

   Reconnect battery

   Reconnect the battery cables.

6. 6

   Clear fault codes

   Connect the Electronic Service Tool (EST) to the machine's diagnostic port. Active codes must be cleared using the EST, or the monitor must execute and pass on three consecutive drive cycles to clear permanent fault codes.