Case IH 51301 – AUX67 / AUX89: On--Board logic voltage out of range Low.

This fault indicates that the internal logic voltage (typically the 5V reference or internal operating voltage) of the controller has dropped below its acceptable operational range. This can be caused by a drop in the main supply voltage to the module, a poor ground connection, a shorted external sensor pulling the reference voltage down, or an internal failure within the controller itself.

• STX Steiger
• STX275
• STX280
• STX325
• STX330
• STX375
• STX380
• STX425
• STX430
• STX440
• STX450
• STX480
• STX500
• STX530
• 280
• 330
• 335
• 380
• 385
• 430
• 435
• 480
• 485
• 530
• 535
• TJ275
• TJ325
• TJ375
• TJ380
• TJ450
• T9000 Series

1. 1

   Verify the main battery voltage and alternator charging system to ensure system voltage does not drop below the operational limit (e.g., 9V) during operation.

2. 2

   Inspect the wiring harness leading to the AUX67 or AUX89 controller for damaged wires, loose connections, or corrosion on the power supply and ground pins.

3. 3

   Check the fuses and relays supplying power to the remote valve controllers (e.g., valve supply relays).

4. 4

   Disconnect any external sensors or potentiometers (like the remote mode lever or flow potentiometers) powered by the controller's logic voltage to see if a shorted component is pulling the voltage down.

5. 5

   If power and ground are within specification and no external shorts exist, evaluate the controller for internal failure.

1. 1

   Safety First

   Disconnect the negative battery cables before working on the electrical system to prevent damage to electronic controllers.

2. 2

   Removal

   Locate the faulty AUX67/AUX89 remote valve controller or valve assembly. Disconnect the wiring harness connectors.

3. 3

   Dismount

   Remove the mounting hardware and extract the faulty unit.

4. 4

   Installation

   Install the replacement controller/valve assembly and secure the mounting hardware.

5. 5

   Reconnection

   Reconnect the wiring harness and the battery cables.

6. 6

   Calibration

   Use the Electronic Service Tool or the tractor's A-post instrument cluster (ARM section) to configure the new controller, calibrate the remote levers (pulling levers back, forward, then to neutral), and clear the stored fault codes.