Case IH F91 – Transmission Control Module (TCM) / Central Controller (XCM): Display Of Gears Controller (CAN Dog) Not Present

This fault code indicates a loss of Controller Area Network (CAN) communication between the main controller and the "CAN DOG" (Display of Gears) module. The system is unable to detect the gear display module on the network, which usually points to a power loss at the display, a wiring harness failure, or a failed display module.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• Puma 140
• Puma 150
• Puma 165
• Puma 180
• Puma 185
• Puma 195
• Puma 200
• Puma 210
• Puma 225
• Maxxum Series
• MX Series (MX100-MX170)
• CX Series

1. 1

   Inspect all cab and transmission control fuses. A blown fuse will cut power to the display, immediately triggering the F91 code.

2. 2

   Verify power and ground at the CAN DOG connector: Pin 1 (Wire 7000BX - U) for Transmission Control Supply (+12V), Pin 2 (Wire 1001AE - W) for Starter Solenoid Feed, and Pin 3 (Wire 57AB - B) for Earth / Ground.

3. 3

   Measure CAN bus voltage at the diagnostic connector (Pins 3 and 4). Abnormal voltages can indicate a shorted CAN wire or a failed Transmission Control Module (TCM) failing to provide the network connection.

4. 4

   Inspect the operator presence switch (seat suspension switch) circuit, which can interrupt the circuit and mimic a dead display module.

1. 1

   Resolve Wiring Issues

   If power, ground, or CAN wires are damaged, repair the wiring harness or clean the ground terminals. Re-test the system.

2. 2

   Replace the Display Module

   If the wiring harness tests good (proper voltage and ground are reaching the connector) but the display remains dead or the F91 code persists, the Display of Gears (CAN DOG) module has failed internally and must be replaced.

3. 3

   Replace the TCM

   If a new display module does not resolve the issue and CAN voltages are out of specification (e.g., missing termination resistors), the Transmission Control Module itself may be faulty and require replacement.

4. 4

   Recalibrate the Transmission

   If the TCM (microprocessor) is replaced, or if the non-volatile memory is reset during the repair, you must perform a Transmission Calibration (Mode HA). Ensure oil is at operating temperature, park on level ground, apply the parking brake, and set engine speed to 1200 RPM before entering calibration mode.