Case IH 12624 – ABS Module / TECU: Rear left wheel speed sensor - air gap

The physical distance (the 'air gap') between the tip of the left rear wheel speed sensor and the tone ring on the axle is out of specification, resulting in a weak, erratic, or missing wheel speed signal.

• Puma
• Magnum
• Optum
• Steiger

1. 1

   Inspect the physical air gap between the rear left wheel speed sensor and the tone ring (typically 0.7 mm or less).

2. 2

   Check the sensor tip and tone ring teeth for mud, dirt, or metallic shavings that could interfere with the magnetic signal.

3. 3

   Inspect the rear left wheel bearing for excessive play or damage, which can cause the axle/tone ring to wobble and fluctuate the air gap.

4. 4

   Ensure the sensor mounting bracket is not loose, bent, or damaged.

5. 5

   Inspect the sensor's wiring harness and connector for corrosion, chafing, or a loose connection.

1. 1

   Park and secure tractor

   Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Locate sensor

   Locate the rear left wheel speed sensor on the rear axle assembly.

3. 3

   Clean area

   Clean the area around the sensor base thoroughly to prevent dirt from falling into the axle housing when the sensor is removed.

4. 4

   Remove sensor

   Unbolt and carefully remove the wheel speed sensor.

5. 5

   Inspect and clean sensor and tone ring

   Inspect the sensor tip. If it is covered in debris or metal shavings, clean it off. Shine a light into the mounting hole and rotate the wheel slowly to inspect the tone ring for missing teeth or heavy grime. Clean if necessary.

6. 6

   Reinstall sensor

   Reinstall the sensor. If the sensor utilizes shims or an adjustable bracket, set the air gap to the manufacturer's specification (ensure it is fully seated if it is a push-in style sensor).

7. 7

   Replace sensor if necessary

   If the sensor is physically damaged, fails a multimeter resistance test, or the code persists after adjusting the gap, replace the sensor with a new unit.

8. 8

   Finalize repair

   Reconnect the wiring harness, clear the fault code using your diagnostic tool, and perform a test drive to confirm the TECU/ABS module is receiving a steady wheel speed signal.