Case IH 51123 – Remote (AUX) Controller: Invalid Software Instruction Executed

The controller has attempted to execute an invalid software command (specifically noted as 'AUX 1 type 1st instance'). The underlying condition is almost always a software glitch or a power/ground interruption that caused the software to fault, though a small chance exists that it is an internal hardware failure.

• MX Magnum
• Case IH MX Magnum series
• Case IH Steiger series

1. 1

   Inspect the controller's connection to the battery, specifically checking connector C053 for a solid connection and proper ground

2. 2

   Clear the fault code from the system

3. 3

   Shut down the tractor completely, wait, and restart it to see if the code returns

1. 1

   Inspect Wiring

   Locate the Remote (AUX) Controller and inspect the main wiring harness, focusing on connector C053. Look for pushed pins, corrosion, or frayed wires that could cause a momentary drop in voltage or ground.

2. 2

   Clean and Secure Connections

   Clean the ground terminals and ensure the battery connections supplying the AUX controller are tight.

3. 3

   Clear the Code

   Use the tractor's diagnostic display or a CAN-bus diagnostic tool to clear the 51123 fault code.

4. 4

   Restart the Machine

   Turn the key off, let the system power down completely, and restart the tractor.

5. 5

   Software Update

   If the code persists after a power cycle, contact your dealer or district Product Support Manager (PSM) to have the AUX controller's software re-flashed or updated.

6. 6

   Hardware Replacement

   If the software update fails or the module is unresponsive, the controller has suffered a hardware failure and must be replaced.