Case IH 12629 – Vehicle Control Unit (VCU), Transmission Control Unit, or ABS ECU: Rear right wheel speed sensor - air gap (no signal)

The control module is not receiving a rotational speed signal from the rear right wheel speed sensor. The system flags this as an "air gap" issue, which typically occurs when the physical distance between the magnetic inductive sensor tip and the tone ring (pole wheel) is too large for the sensor to read the passing teeth, or there is a complete loss of signal due to an electrical open circuit.

• CVT Series 6130
• CVT Series 6145
• CVT Series 6160
• CVT Series 6165
• CVT Series 6180
• CVT Series 6200
• CVT Series 6210
• CVT Series 6225
• CVT Series 6170
• CVT Series 6185
• CVT Series 6205
• CVT Series 6215
• CVT Series 6230
• PROFI Series 4110
• PROFI Series 4120
• PROFI Series 4130
• PROFI Series 6115
• PROFI Series 6125
• PROFI Series 6140
• 9080 MT
• 9085 MT
• 9090 MT
• 9095 MT
• 9100 MT
• 9105 MT
• Puma Series
• Magnum Series

1. 1

   Visually inspect the sensor mounting for rust, mud, or debris buildup that can lift the sensor away from the tone ring.

2. 2

   Inspect the tone ring (pole wheel) through the mounting hole to verify it is not loose, heavily coated in metallic debris, or missing teeth.

3. 3

   Disconnect the sensor and inspect the harness connector for moisture, corrosion, or pushed-out pins.

4. 4

   Test the sensor harness for continuity back to the ECU to rule out a broken wire (open circuit) or a short to ground.

1. 1

   Secure the Machine

   Park the tractor on a level surface, engage the parking brake, and turn off the battery disconnect switch.

2. 2

   Locate the Sensor

   Locate the rear right wheel speed sensor on the rear axle housing/hub.

3. 3

   Remove the Sensor

   Disconnect the electrical pigtail. Remove the retaining bolt holding the sensor in place. Carefully twist and pull the sensor out of the bore.

4. 4

   Clean the Bore

   Thoroughly clean the sensor bore and the flat mounting surface on the axle housing. Crucial step: If rust scale is left on the mounting surface, the new sensor will not seat fully, and the "air gap" fault will immediately return.

5. 5

   Install New Sensor

   Insert the replacement wheel speed sensor. Torque the retaining bolt to OEM specifications.

6. 6

   Reconnect and Route Wiring

   Plug the sensor back into the chassis harness. Ensure the wire is routed safely away from moving parts and secured with zip ties.

7. 7

   Clear Codes and Test

   Power on the tractor, clear the inactive 12629 fault code via the diagnostic monitor, and perform a short test drive to verify the ECU is registering rear right wheel speed.