Case IH 35 – Instrumentation Controller (ICU / ICU2): Slip Sensor (radar or wheel speed) is failed in the Instrumentation Controller

The instrumentation controller detects a failure in the wheel slip sensing circuit (usually a failed radar gun or wheel speed sensor) or, less commonly, when the percent slip calculation fails internally within the controller.

• Magnum
• Case IH Steiger & STX Series 4WD Tractors
• Case IH MX Magnum Series
• Case IH Maxxum Series
• Case IH Puma Series

1. 1

   Monitor Diagnostics: If equipped with a Pro600 or Pro700 monitor, navigate to Diagnostics --> Speed. Compare vehicle speed readings from the radar, transmission speed sensor, and GPS to identify which sensor has dropped out.

2. 2

   Bypass Test: Unplug the radar unit. If the speedometer starts working again (defaulting to the transmission wheel speed sensor), the radar unit or its immediate wiring is the culprit.

3. 3

   Pinout & Voltage Checks at the Radar Connector: Test the 4-pin weather-pack connector. Pin A (Ground) should have continuity to clean ground (SPL-F1). Pin C (Power) should have +12V B+ supply from Fuse 34.

4. 4

   Check Radar Presence and Signal: Verify Pin D returns +12V to the controller (indicating radar presence). Verify Pin B (Signal) outputs a square wave form (Low <= 0.8 VDC, High >= 3.7 VDC) with a frequency scaled to 44 Hz/mph while moving.

1. 1

   Inspect the Harness

   Check the wiring harness leading to the radar sensor (usually mounted under the cab or on the chassis) and the transmission wheel speed sensor for chafing, corrosion, or rodent damage. Repair any broken wires.

2. 2

   Test the Sensor

   Perform the pinout voltage checks. If Pin A has good ground and Pin C has 12V power, but Pin D does not return 12V or Pin B outputs no frequency while moving, the radar sensor has failed internally and must be replaced.

3. 3

   Replace the Sensor

   Disconnect the 4-pin connector, unbolt the faulty radar gun or wheel speed sensor from its mounting bracket, and install the replacement part. (Note: Case IH recommends replacing older Vansco 'hockey puck' style radar units with the square Dickey-John units).

4. 4

   Calibrate the New Sensor

   After replacing a speed or radar sensor, it must be calibrated to the Electronic Management Unit. Mark out a 100-meter track. Enter the H-Menu calibration mode (on some models, this is done by holding both the manual FWD and Differential Lock touchpads while starting the tractor). Drive the 100m track as per the on-screen prompts to teach the ICU the correct pulses-per-meter.