Case IH 15993 - AST – AST (Auto Steering): NAV not present but configured

CAN bus communication issue. The vehicle's Auto Steering (AST) module or main controller is software-configured to expect a Navigation Controller (NAV II, NAV III, or NAV-900) on the network for the AFS AccuGuide auto-guidance system, but it is not receiving any communication from the NAV unit.

• MAXXUM T4E
• VESTRUM CVX
• Magnum series
• Steiger series
• Puma series
• Optum series
• Maxxum series
• Axial-Flow series (7120, 8250, 9120)
• Patriot series

1. 1

   Verify if the machine actually has a Navigation Controller installed (this fault frequently occurs when a display is moved between machines or incorrectly configured).

2. 2

   Inspect the fuse panel for blown fuses supplying power to the GPS/Navigation system.

3. 3

   Locate the NAV controller (Nav II/III inside cab under floor mat/seat; NAV-900 roof-mounted) and check the main Deutsch/Amphenol connectors for corrosion, moisture, or pushed-out pins.

4. 4

   Using a multimeter, verify that the NAV controller is receiving steady 12V power and has a clean ground at the harness connector.

5. 5

   With the battery disconnected, measure the resistance across the CAN High and CAN Low pins at the NAV connector (should read approximately 60 ohms; 120 ohms indicates an open circuit, 0 ohms indicates a short).

1. 1

   Turn on the key and allow the AFS Pro 700 / Pro 1200 display to boot up.

   Scenario A: The machine does NOT have a NAV controller.

2. 2

   Navigate to Toolbox > NAV (or Toolbox > System, depending on firmware version).

3. 3

   Locate the Navigation Controller configuration setting.

4. 4

   Change the setting from "Installed" to "Not Present" or "None".

5. 5

   Cycle the key power. The fault code should clear.

6. 6

   Cycle the machine's battery disconnect switch to perform a hard reset of the NAV controller.

   Scenario B: The machine DOES have a NAV controller. Perform this if power, ground, and CAN bus wiring tested perfectly in the diagnostic phase, as the NAV controller may be stuck in a diagnostic or simulation loop.

7. 7

   Connect the Case IH Electronic Service Tool (EST) laptop to the diagnostic port.

8. 8

   Attempt to ping the NAV controller. If it responds, re-flash the NAV controller with the latest firmware.

9. 9

   If the EST cannot communicate with the NAV controller at all (and the harness is verified good), the NAV controller has suffered an internal hardware failure and must be replaced.

10. 10

    Install the new NAV controller, calibrate the steering (Wheel Angle Sensor, Roll/Pitch/Yaw), and clear the fault codes.