Case IH 12612 – Transmission Controller (TRANS): Rear left wheel speed sensor - shorted to ground

A "shorted to ground" error indicates that the voltage supply or signal wire for the wheel speed sensor has an unintended direct electrical path to the chassis ground (0 volts). This pulls the signal voltage down, preventing the control module from reading the rotational speed of the wheel. This loss of data can disable functions like traction control, ABS, or transmission speed matching.

• Magnum Series (e.g., 235-340, 7110, 7120)
• Steiger Series (e.g., STX 350-600)
• MX / TG Series (e.g., MX100 to MX305)
• Puma Series (e.g., Puma 125, 210)
• CS and CVX Series

1. 1

   Inspect the wiring harness leading to the rear left wheel speed sensor for chafing, melting, or pinching against the chassis that could cause a short to ground.

2. 2

   Disconnect the sensor and check the pins for corrosion, moisture, or damage.

3. 3

   Use a multimeter to check the signal and supply wires for continuity to ground. If the wire shows continuity to ground while disconnected from both the sensor and the ECU, the wiring harness is shorted and must be repaired.

4. 4

   Verify the 5V internal reference voltage from the transmission controller.

1. 1

   Secure the Machine

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

2. 2

   Locate the Sensor

   Locate the rear left wheel speed sensor on the axle housing or final drive assembly.

3. 3

   Disconnect Wiring

   Unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Remove the retaining bolt(s) holding the sensor in place. Carefully pull the sensor straight out of its bore.

5. 5

   Clean the Mounting Surface

   Ensure the bore and mounting surface are free of dirt and rust to ensure the new sensor seats at the correct depth (sensor gap tolerance is critical for accurate speed readings).

6. 6

   Install New Sensor

   Insert the replacement sensor, then install and tighten the retaining bolt.

7. 7

   Reconnect and Route Wiring

   Plug in the electrical connector. Ensure the harness is routed away from moving parts and secured with zip ties to prevent future chafing.

8. 8

   Clear Codes and Test

   Turn on the ignition, clear the fault codes from the Transmission controller, and perform a test drive to verify the speed signal is restored and the code does not return.