Case IH 12609 – Transmission Control Unit (TCU), Vehicle Control Unit / Instrument Cluster Unit (ICU), or ABS Module: Rear right wheel speed sensor - open circuit or shorted to battery

This fault indicates a critical electrical failure in the circuit for the rear right wheel speed sensor. This can be caused by an open circuit (a physical break in the wiring, a blown fuse, or a disconnected/corroded plug) or a short to battery (the sensor's signal or ground wire is chafed and making direct contact with a positive voltage source).

• Magnum Series (180, 200, 220, 240, 250, 280, 310, 340, 380)
• Maxxum Series (115, 125, 135, 145, 150)
• Puma Series (150, 165, 185)
• Farmall Series (50A, 60A, 70A)
• Steiger Series
• Legacy MX Series (MX100, MX135, MX255)

1. 1

   Inspect Wiring: Check the wiring harness leading to the rear right axle for chafing, breaks, or pinched wires.

2. 2

   Check Connections: Disconnect the sensor plug and inspect the pins for corrosion, dirt, or water ingress.

3. 3

   Test Sensor Output: Use a multimeter to test the sensor output at various speeds.

4. 4

   Check Sensor Position: Ensure the sensor is positioned correctly relative to the tone ring (the toothed gear it reads). If the gap is too large or misaligned, it will fail to read.

1. 1

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

2. 2

   Disconnect the electrical connector from the sensor.

3. 3

   Remove the mounting hardware (usually a single bolt) and carefully pull the sensor out of the housing.

4. 4

   Clean the mounting surface to ensure the new sensor sits flush.

5. 5

   Install the new sensor, ensuring it is positioned just right relative to the tone ring.

6. 6

   Reconnect the wiring harness, ensuring the plug clicks securely into place.

7. 7

   Clear the fault codes from the system using a diagnostic tool or the AFS Pro display.

8. 8

   Test drive the tractor to verify that the ground speed displays correctly on the A-post/monitor and that the transmission shifts smoothly without throwing the code again.