John Deere 191 – Transmission Control Unit: Transmission Speed During Calibration Too High / Transmission Overspeed

The transmission output speed sensor is detecting a rotational speed that is too high for the current operating state. This typically happens when the tractor is overspeeding downhill, rolling during calibration, or if the transmission speed sensor is defective.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5045E
• 5055E
• 5065E
• 5075E
• 5085E
• 5090E
• 5100E
• 7720
• 7820
• 7920
• 7430
• 7530
• 7185J
• 7195J
• 7205J
• 7210J
• 7225J

1. 1

   Check operational context: Verify if the operator was coasting in neutral or driving downhill with a heavy implement when the code triggered.

2. 2

   Check calibration environment: If the code triggered during a transmission calibration, verify that the tractor is parked on a completely level surface and the parking brake is firmly set.

3. 3

   Inspect sensor and wiring: Locate the transmission output speed sensor (e.g., B104, B172, B66, or B31). Inspect the wiring harness and connector for damage, corrosion, or short/open circuits.

1. 1

   Operational reset

   If the code was caused by coasting downhill, slow the vehicle down and use engine braking. Restart the tractor to reset the communication messages; the code will often clear itself if the overspeed condition is no longer present.

2. 2

   Recalibrate transmission

   If the code triggered during calibration, move the tractor to a flat, level surface. Apply the parking brake securely so the vehicle cannot roll, and repeat the transmission calibration procedure.

3. 3

   Replace transmission output speed sensor

   If the code persists while the tractor is stationary and the wiring is intact, the transmission output speed sensor is likely defective. Disconnect the wiring harness, remove the retaining bolt, and pull the sensor out of the transmission housing. Install the new sensor, secure the bolt, and reconnect the wiring harness. Clear the fault codes via the CommandCenter or diagnostic tool and perform a transmission calibration.