Case IH 51302 – AUX67 Controller: On-Board logic voltage out of range High.

The internal logic circuit of the controller is detecting a voltage level that exceeds its maximum allowable threshold. This condition is typically caused by a short to power in the wiring harness, a severely degraded ground connection, an overcharging alternator, or an internal failure of the controller's logic board.

• STX Steiger
• STX275
• STX280
• STX325
• STX330
• STX375
• STX380
• STX425
• STX430
• STX440
• STX450
• STX480
• STX530

1. 1

   Test system voltage at the battery and alternator output while the tractor is running to ensure the alternator is not overcharging (voltage should not exceed ~14.5V).

2. 2

   Inspect the wiring harness leading to the rear remote valve stack (specifically sections 6 and 7). Look for chafed wires, melted insulation, or any areas where the controller's sensor/logic wires might be shorting directly to a 12V power source.

3. 3

   Check the ground connections for the remote valve controllers. Clean and tighten the ground terminals, as a loose, corroded, or broken ground can cause the internal logic voltage to read artificially high.

4. 4

   Connect the Case IH Electronic Service Tool (EST) to monitor the live logic voltage data for the AUX67 controller. If the harness and grounds test perfectly but the EST still shows the logic voltage out of range, the controller has an internal failure.

1. 1

   Power Down

   Turn off the tractor and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Valve Stack

   Locate the remote hydraulic valve stack at the rear of the tractor. Identify the controller for sections 6 & 7 (AUX67).

3. 3

   Disconnect

   Carefully unplug the electrical harness connectors from the faulty remote valve controller.

4. 4

   Remove the Controller

   Unbolt the auxiliary hydraulic control unit from the valve stack assembly. Be prepared to catch a small amount of residual hydraulic fluid.

5. 5

   Install the New Unit

   Mount the replacement remote valve controller to the stack, ensuring all O-rings/seals are properly seated. Torque the mounting bolts to OEM specifications.

6. 6

   Reconnect

   Reconnect the electrical harness and the battery.

7. 7

   Calibrate

   Connect the Case IH Electronic Service Tool (EST). You must use the EST to calibrate the new remote hydraulics controller and clear the 51302 fault code from the system memory.