Case IH 12631 – ABS Module or Frame ECU / Vehicle Control Module: Front right wheel speed sensor - air gap (no signal)

The control module is not receiving a rotational speed signal from the front right wheel speed sensor because the air gap is either too large, obstructed by debris, or the sensor has failed entirely.

• Magnum
• Puma
• Maxxum
• Steiger
• Optum
• MX150
• MX170
• Early Riser Planters

1. 1

   Inspect the front right wheel hub area for heavy mud, crop debris, or ice packed around the sensor head that could obstruct the magnetic field.

2. 2

   Check the air gap between the sensor tip and the toothed wheel (standard gap is 0.020 - 0.040 in or 0.5 - 1.0 mm).

3. 3

   Rotate the front right wheel manually and inspect the tone ring through the sensor port for missing, bent, or heavily rusted teeth.

4. 4

   Disconnect the sensor and check the 3-pin connector for corrosion, moisture, or backed-out pins.

5. 5

   Trace the wiring harness back to the Frame ECU/ABS module to ensure there are no chafed or broken wires.

1. 1

   Preparation

   Park the machine on a level surface, engage the parking brake, and turn off the engine. If necessary for access, safely lift and support the front right axle.

2. 2

   Removal

   Locate the front right wheel speed sensor on the steering knuckle/hub assembly. Disconnect the electrical pigtail from the main wiring harness.

3. 3

   Extraction

   Remove the retaining bolt holding the sensor in place. Carefully twist and pull the sensor out of its mounting bore. (If it is seized, use penetrating oil; do not pry aggressively to avoid breaking the plastic housing inside the hub).

4. 4

   Cleaning

   Thoroughly clean the mounting surface and the bore hole. Any rust or dirt buildup on the mounting pad will push the new sensor outward, creating an excessive air gap and causing the new sensor to fail immediately.

5. 5

   Installation

   Insert the new wheel speed sensor. If the sensor utilizes shims for adjustment, set the air gap to 0.020 - 0.040 in (0.5 - 1.0 mm).

6. 6

   Reassembly

   Install and tighten the retaining bolt. Reconnect the electrical harness and secure the cable with zip ties to prevent it from rubbing against moving suspension parts.

7. 7

   Validation

   Turn on the machine, clear the stored 12631 fault code via the diagnostic display (e.g., AFS Pro 700), and perform a short test drive to verify the speed signal is registering correctly.