Case IH A-G-553 - Display – Display: Guidance Speed Disparity

There is a mismatch between the vehicle's physical speed (reported by the transmission/wheel speed sensors) and the GPS ground speed calculated by the GNSS receiver.

• MAGNUM AFS Connect
• STEIGER AFS Connect
• Steiger
• Puma
• Optum
• Axial-Flow

1. 1

   Check Satellite Convergence: Ensure sufficient DGPS position data is present by checking the count of available satellites on the AFS display and waiting for convergence.

2. 2

   Verify Receiver Mounting: Ensure that the NAV controller and GNSS receiver are secured in the proper location and orientation on the cab roof. A loose receiver will cause erratic heading calculations.

3. 3

   Perform a Dynamic Test: Drive a short distance at medium speeds to provide vehicle heading and see if the speed disparity or heading error clears.

4. 4

   Check Software Status: Verify that software version information from the NAV controller is being successfully obtained by the display.

1. 1

   Connect Diagnostic Tool

   Connect the Case IH Electronic Service Tool (EST) via a protocol adapter to the vehicle's CAN bus to retrieve controller status, parameter monitoring, and freeze-frame data for the A-G fault.

2. 2

   Inspect Hardware

   Climb to the cab roof and physically inspect the GNSS receiver (e.g., Vector Pro) and NAV controller. Tighten any loose mounting brackets.

3. 3

   Inspect Wiring

   Check the wiring harness and connectors between the GNSS receiver, the NAV controller, and the AFS Display for corrosion, moisture, or damaged pins.

4. 4

   Clear and Calibrate

   Use the Customer EST or the AFS Display to clear the fault code. Perform a steering/guidance calibration drive as outlined in the operator's manual.

5. 5

   Component Replacement

   If the receiver fails to acquire a heading or speed after physical inspection and software clearing, the internal IMU/GPS module has likely failed. Replace the GNSS receiver/NAV controller and use the EST software to "pair" the new part to the machine's CAN network.