Case IH 708-19 - ACM – ACM: Throttle keypad disconnected

Communication failure, open circuit, or signal drop-out between the throttle input device (keypad or potentiometer) and the control network. The module is no longer receiving the expected voltage or data packets from the throttle control.

• MAGNUM AFS Connect
• Magnum series
• Magnum 235–340
• Steiger/STX series
• STX425
• Puma
• Optum
• Maxxum

1. 1

   Monitor the throttle signal using a diagnostic laptop (EST) to see if the signal is failing for a split second and triggering the lockout alarm.

2. 2

   Check the CAN bus voltage. The CAN bus runs on a nominal 2.5 VDC (one leg should read around 2.45V and the other 2.55V).

3. 3

   Inspect the throttle potentiometer/keypad for alignment issues or open circuits.

4. 4

   Check the CAN bus terminators to ensure they have not failed, which can cause modules to go offline.

1. 1

   Test CAN terminators

   Unplug the CAN terminators one at a time; if the system comes back online when one is unplugged, that terminator has failed and must be replaced.

2. 2

   Inspect and clean wiring

   Inspect and clean the wiring harness connectors between the throttle keypad and the Armrest Control Module (ACM).

3. 3

   Recalibrate throttle

   Recalibrate the throttle control using the tractor's diagnostic interface.

4. 4

   Replace throttle assembly

   If the signal continues to drop out and the wiring is intact, replace the throttle assembly.

5. 5

   Replace ACM

   If replacing the throttle does not restore communication, the ACM itself may have an internal hardware failure and will need to be replaced.