Case IH NH3088 – Transmission Control Unit (TCU) or Vehicle/Chassis Control Unit: Increment Speed Signal - Not Plausible

The system has detected that the increment speed signal is not plausible, indicating an inconsistency or error in the speed signal input. The signal from a speed sensor is inconsistent or outside of its expected range, which can cause erratic speedometer readings or transmission shifting issues.

• 3088
• 3288
• 3488
• 3688
• 2144
• 2166
• 2188
• 2344
• 2366
• 2377
• 2388
• 2577
• 2588

1. 1

   Visually inspect the relevant speed sensor and its wiring harness for frayed wires, loose connections, or corrosion

2. 2

   Check for metallic debris on the magnetic tip of the speed sensor, which can interfere with its reading

3. 3

   Disconnect the sensor and inspect the connector pins for a secure fit and any signs of corrosion or damage. Clean as necessary.

4. 4

   Test the wiring harness for continuity and check for any short circuits to ground or power

5. 5

   Use a multimeter to test the sensor's resistance and compare it to manufacturer specifications, or check for AC voltage output while rotating the monitored component

1. 1

   Identify the faulty sensor

   Based on the machine's symptoms (e.g., erratic speedometer, transmission shifting issues), identify the specific speed sensor that is likely causing the fault (e.g., ground speed, transmission speed, PTO speed).

2. 2

   Access the sensor

   Safely gain access to the sensor. This may require removing panels or other components.

3. 3

   Perform diagnostic checks

   Follow the diagnostic checks to rule out a wiring or connection issue before condemning the sensor.

4. 4

   Replace the sensor

   If the sensor is determined to be faulty, unscrew it from its mounting position. Install the new sensor, ensuring it is threaded in to the correct depth.

5. 5

   Reconnect and test

   Securely connect the wiring harness to the new sensor. Start the machine and check if the fault code has cleared and if the related function is operating correctly.