Case IH PB1 – Transmission Control Module (TCM): Vehicle CAN Chip, Shorted To High Source

The CAN transceiver chip has detected a short circuit to a high voltage source (typically 12V battery power) on the vehicle's CAN bus communication lines. This prevents the module from communicating properly with other systems on the tractor. Note: The fault code displayed on the dash is actually tB1 (or TB1), but the digital display font often causes the lowercase 't' to be misread as a 'P'.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190

1. 1

   Turn off the tractor and disconnect the battery to prevent further module damage

2. 2

   Visually inspect the transmission wiring harness for chafing, melted insulation, or pinched wires that could be bridging a 12V power wire to the CAN High or CAN Low wires

3. 3

   Disconnect the harness from the TCM and use a multimeter to check the CAN High and CAN Low pins on the harness side for continuity to any 12V power source

4. 4

   Measure the resistance across the CAN High and CAN Low pins on the harness (a healthy CAN bus should read approximately 60 ohms)

5. 5

   If the wiring harness tests perfectly fine with no shorts to power, verify internal failure of the Transmission Control Module (the CAN chip itself has burned out or shorted)

1. 1

   Disconnect battery

   Disconnect the negative battery cable.

2. 2

   Remove TCM

   Locate and remove the Transmission Control Module (usually located in the cab console or under the right-hand trim, depending on the exact cab configuration).

3. 3

   Install TCM

   Install the replacement or remanufactured TCM.

4. 4

   Configure controller

   Configuration (H8 Operation): You must reconfigure the new controller to the correct transmission type to identify the tractor model. If not configured, the display will show a 'C0' fault code.

5. 5

   Calibrate transmission

   Calibration: Once configured, warm up the tractor (engine speed to 1200 RPM) and perform a full transmission clutch calibration so the new module can learn the clutch fill times.