John Deere 191.31 – CCU: Transmission Output Speed Fault

The control unit is either not receiving the expected transmission output speed signal over the CAN bus, or the broadcasted message is missing/invalid due to a sensor failure or a communication breakdown on the powertrain CAN bus.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6090MC
• 6090RC
• 6100MC
• 6100RC
• 6110MC
• 6110RC

1. 1

   Inspect the transmission output speed sensor (located on the transmission housing/rear axle area) for physical damage, heavy debris, or loose connections

2. 2

   Inspect the CAN bus wiring harness between the CCU and the transmission output speed sensor for chafed, broken, or corroded wires

3. 3

   Verify the CAN bus terminating resistors and check the CAN High and CAN Low voltage levels (typically around 2.5V) to ensure proper bus communication

4. 4

   Look for other active CAN bus codes (e.g., CCU 000247.09) which might indicate a broader network failure rather than an isolated sensor issue

1. 1

   Disconnect Power

   Disconnect the tractor's battery power before servicing electrical components.

2. 2

   Clean and Reseat

   Disconnect the wiring pigtail at the transmission output speed sensor. Clean the contacts with electrical contact cleaner, apply dielectric grease, and reseat the connector. Re-test the machine.

3. 3

   Repair Wiring

   If any damage was found in the CAN bus harness during diagnostics, repair the broken or shorted wires using OEM-approved splicing methods.

4. 4

   Replace the Sensor

   If the wiring is intact and the CCU is functioning normally, the transmission output speed sensor has likely failed internally. Remove the retaining bolt/locking ring, pull the old sensor out of the transmission housing, and install the new sensor. (Note: Some sensors require threading in until they contact the tone ring, then backing out 1/2 to 1 full turn before locking down.)

5. 5

   Clear Codes

   Reconnect the battery, clear the inactive fault codes via the diagnostic monitor, and test drive the tractor to verify that the transmission speed registers correctly and the code does not return.