Case IH 15996 – MTA CCM or APH: Autoguidance Engage/Variable Ratio Activation switch - open circuit or short circuit to ground

This code indicates a hard electrical fault (either a broken wire/disconnected plug or a wire rubbing against the chassis) in the circuit for the switch used to engage the AFS AccuGuide autoguidance system or variable ratio steering.

• MAXXUM T4E
• VESTRUM CVX
• Case IH Maxxum series
• Case IH Puma series
• Case IH Magnum series
• Case IH Steiger series

1. 1

   Visually inspect the Autoguidance Engage switch (on the armrest console or Multi-Function Handle) for physical damage, sticking, or liquid intrusion

2. 2

   Inspect the wiring harness running from the armrest console/MFH to the MTA CCM/APH controller for pinched wires, chafing against the seat suspension frame, or disconnected plugs

3. 3

   Disconnect the switch and test for continuity across the switch terminals when pressed using a multimeter

4. 4

   Test the harness side for continuity to ground to isolate a short circuit, and test for an open circuit between the switch connector and the cab controller pins

5. 5

   Connect the Case IH Electronic Service Tool (EST), navigate to Automatic Guidance System II AccuGuide > Diagnostic Serial Connector, and monitor the live state of the Autoguidance Engage switch to see if the controller registers the button press or defaults to an unexpected value

1. 1

   Power Down

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

2. 2

   Access the Switch

   Carefully remove the trim panels on the armrest console or disassemble the Multi-Function Handle (depending on your specific model's switch location) to access the back of the Autoguidance Engage switch.

3. 3

   Test/Replace the Switch

   Unplug the switch connector. If the switch failed the multimeter continuity test in the diagnostic phase, replace the switch with a new OEM unit.

4. 4

   Repair Wiring (If Applicable)

   If the switch is functional, trace the wiring down the armrest pivot point (a common area for wire chafing). Splice and heat-shrink any broken or exposed wires causing the short/open circuit.

5. 5

   Reassembly

   Reconnect the switch and reassemble the armrest console or MFH.

6. 6

   Clear Codes and Calibrate

   Reconnect the battery. Use the EST or the AFS Pro display to clear the 15996 fault code. You may need to perform a quick steering calibration or press the autoguidance engage switch to verify the system registers the "MoVe" instruction and successfully engages.