Case IH tB6 – PCU (Powertrain Control Unit) or Electronic Engine Control Unit (ECU): CAN VE Message (Speed Set point), Data Valid But Above Normal Range

The control unit is receiving a CAN bus message regarding the vehicle's speed set point (VE message). While the data format is valid and recognized by the system, the actual value being reported is above the normal operating parameters. This typically indicates a sensor failure (such as a potentiometer or speed sensor sending a high voltage/resistance value), a wiring short to a high-voltage source, or a system calibration error.

• MXM
• Case IH MXM 120
• Case IH MXM 130
• Case IH MXM 140
• Case IH MXM 155
• Case IH MXM 175
• Case IH MXM 190
• Case IH Maxxum
• Case IH Puma

1. 1

   Inspect the CAN bus wiring between the speed sensors, the speed set point potentiometer, and the PCU for chafed wires, corrosion, or bent pins causing a short to a high-voltage source.

2. 2

   Test the gear change / range command potentiometer (speed set point rotary position sensor) with a multimeter to verify it receives a 13.5 VDC reference voltage and its resistance sweeps smoothly up to 4000 Ohms.

3. 3

   Check the inductive magnetic speed sensor on the transmission housing or flywheel bell housing to ensure it is securely mounted and free of metallic debris.

4. 4

   Check calibration status, as recent mechanical repairs, disconnected potentiometers, or memory resets can cause out-of-range codes until recalibrated.

1. 1

   Safety Setup

   Park the tractor on level ground. Place all shift levers in neutral, block the front and rear wheels, and turn off the engine.

2. 2

   Clean and Reconnect

   Disconnect the harnesses at the speed set point potentiometer and the transmission speed sensor. Clean the contacts with electronic contact cleaner, apply dielectric grease, and reconnect. Turn the key ON to see if the tB6 code clears.

3. 3

   Replace Faulty Component

   If the potentiometer is faulty: Remove the mounting hardware, unplug the harness, install the new rotary position sensor, and secure it. If the speed sensor is faulty: Remove the retaining hex screw (usually an M6 x 14mm), pull the old inductive sensor out of the transmission housing, insert the new sensor, and tighten the screw.

4. 4

   Recalibrate the Transmission/PCU

   Start the engine and ensure the transmission oil is at operating temperature (between 10°C and 105°C). Enter calibration mode (on MXM models, this is typically done by holding the High and Low range buttons simultaneously while starting the engine until 'CAL' appears on the display). Set the engine speed to 1200 RPM. Follow the on-screen prompts to calibrate the clutches and potentiometers. The display will show 'END' or 'CF' (Calibration Procedure Completed Successfully) when finished.

5. 5

   Final Test

   Cycle the key switch off and back on. Test drive the tractor to verify that the speed set point functions correctly and the tB6 code does not return.