Case IH t38 – Transmission Control Module: Vehicle CAN Bus Transmit, Data Valid But Above Normal Range

The control module is successfully transmitting data across the tractor's Controller Area Network (CAN) bus, and the data format is valid, but the actual values being transmitted exceed the normal operating parameters expected by the system.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• MX/TG

1. 1

   Inspect the CAN Bus wiring harness for physical damage, chafing, or internal wire breaks, especially where the harness routes near the armrest.

2. 2

   Test the active CAN terminators located behind the rear cab cover and in the engine bay for broken solder joints or loose pins.

3. 3

   Measure CAN Bus voltage on the data lines using a multimeter; both CAN High (yellow) and CAN Low (green) wires should read around 2.4 to 2.5 volts.

4. 4

   Check the multi-pin connections at the Transmission Control Module to ensure they are seated tightly and free of corrosion.

1. 1

   Disconnect Power

   Always disconnect the battery before servicing the tractor's CAN bus or ECUs.

2. 2

   Repair Wiring/Terminators

   If the diagnostic checks reveal a broken wire or a faulty CAN terminator, splice/repair the wiring harness or replace the terminator plug.

3. 3

   Replace the Transmission Control Module

   If the wiring, voltages, and terminators are all intact, the Transmission Control Module itself is likely failing to process data correctly and must be replaced.

4. 4

   Perform Transmission Calibration

   If the Transmission Control Module is replaced (or if its non-volatile memory is reset), you must perform a transmission and clutch calibration. Warm the transmission fluid to between 20°C and 50°C. Apply the parking brake, turn off the AC, and deselect all electrical/hydraulic services. Enter the 'H-Menu' calibration mode (H1 for Clutch and Synchroniser). Set the engine speed to 1200 RPM. Follow the dashboard display prompts to allow the system to calibrate the clutch packs.