Case IH 3020 – Instrumentation Controller (INST): Slip Sensor (radar or wheel speed) has failed

The slip sensor is responsible for measuring the actual ground speed of the tractor. The controller compares this ground speed to the transmission/wheel speed to calculate wheel slip, which is critical for automatic draft control, hitch adjustments, and transmission management. When this signal is lost, erratic, or out of range, the system disables slip-dependent features and logs the code.

• MX Magnum
• STX Steiger
• MX Magnum Series
• TG Series
• STX and Steiger 4WD Series
• Puma Series
• Maxxum Series

1. 1

   Check for Electromagnetic Interference (EMI) from high-power electrical devices (transformers, radios, cell phones) that can cause electronic interference on the radar/speed sensing circuit.

2. 2

   Check for related Transmission (TRANS) or Hitch fault codes, which may point to a shared ground or wiring harness issue rather than a failed sensor.

3. 3

   Inspect the wiring harness leading to the radar or wheel speed sensor for chafed wires, corrosion in the 3-pin connector, or physical damage from field debris.

4. 4

   Verify that the sensor is receiving proper reference voltage from the controller and check the signal wire for continuity back to the Instrumentation Controller.

1. 1

   Locate the Sensor

   Park the tractor on a level surface, turn off the engine, and remove the key. Identify whether your machine uses a radar ground speed sensor (typically mounted on a bracket under the cab/chassis pointing toward the ground) or a magnetic wheel speed sensor (mounted directly on the transmission or axle housing).

2. 2

   Disconnect Wiring

   Carefully unplug the electrical connector from the sensor, ensuring you do not break the locking tab.

3. 3

   Remove the Sensor

   For a radar sensor: Unbolt the sensor from its mounting bracket. For a wheel speed sensor: Remove the retaining bolt and carefully pull the sensor out of the housing (be prepared for a small amount of oil seepage depending on the location).

4. 4

   Install the New Sensor

   For a radar sensor: Bolt the new sensor to the bracket. Ensure the mounting angle and height match the OEM specifications, as radar sensors require a specific trajectory to read the ground accurately. For a wheel speed sensor: Lubricate the O-ring (if applicable), seat the sensor fully into the housing, and tighten the retaining bolt.

5. 5

   Reconnect and Calibrate

   Reconnect the wiring harness. Turn the key on, clear the fault codes, and perform the ground speed/slip sensor calibration procedure as outlined in your specific model's operator manual.