Case IH 15226 - AST – AST (Advanced Steering) / Steering Valve Controller (SVC): Steering valve controller - 5 Volt supply too low

This fault code indicates that the 5-volt reference supply generated by the steering valve controller is dropping below the acceptable threshold. A "too low" condition usually points to a short to ground in the sensor wiring, a failed sensor pulling the voltage down, or an internal failure within the controller itself.

• MAXXUM T4E
• VESTRUM CVX
• AFS Connect Magnum 180
• AFS Connect Magnum 200
• AFS Connect Magnum 220
• AFS Connect Magnum 240
• AFS Connect Magnum 250
• AFS Connect Magnum 280
• AFS Connect Magnum 310
• AFS Connect Magnum 340
• AFS Connect Magnum 380
• Vestrum CVX 100
• Vestrum CVX 110
• Vestrum CVX 120
• Vestrum CVX 130
• Puma
• Maxxum
• Optum
• Farmall 40-50
• Farmall 115U

1. 1

   Sensor Isolation: Disconnect the steering sensors (e.g., steering wheel sensor, cut-off solenoids) one at a time. If the 5V reference voltage returns to normal at the controller pin after unplugging a specific sensor, that sensor is internally shorted and must be replaced.

2. 2

   Wiring Harness Inspection: Inspect the wiring harness between the Steering Valve Controller and the steering sensors. Look for chafing, pinched wires, or corrosion that could cause the 5V reference wire to short to the chassis ground or a ground wire.

3. 3

   Controller Power & Ground: Verify that the Steering Valve Controller itself is receiving proper battery voltage and has a clean, low-resistance ground.

4. 4

   Controller Output Test: If the wiring harness is completely isolated (unplugged from all sensors) and the controller still fails to output 5 Volts on the reference pin, the controller has an internal hardware failure.

1. 1

   Resolve the Short

   Repair any damaged sections of the wiring harness or replace the internally shorted sensor identified during the diagnostic checks.

2. 2

   Replace Controller (If necessary)

   If the controller is internally faulty, disconnect the battery, remove the hydraulic steering valve controller unit, and install the replacement module.

3. 3

   Clear Codes

   Use the Electronic Service Tool (EST) or the tractor's on-board instrument cluster to clear the fault. To access the on-board diagnostics via the cluster: Navigate the "H menus" using the switches on the instrument cluster. Go to the R1 module, select menu H3, and select the AST system to view and clear the subsystem codes.

4. 4

   Recalibrate

   If the steering valve controller or a steering sensor was replaced, you must perform the AST Steering Calibration procedure before returning the tractor to service.