Kubota E-6 – Power Train ECU / Transmission ECU: Shuttle sensor main/sub phase shifting trouble

This code indicates a discrepancy or phase-shifting error between the main and sub signals of the shuttle sensor, which monitors the position of the shuttle lever (forward/neutral/reverse). When this occurs, the tractor's safety protocols may prevent the related solenoid valves from operating, resulting in a loss of forward or reverse drive.

• M4-071
• M5-091
• M5-111
• M5N-091
• M5N-111
• M6-101
• M6-111
• M6S-111
• M95X
• M105X
• M125X

1. 1

   Check the voltage at the shuttle sensor wiring harness. The reference voltage should be 5 volts.

2. 2

   Enter the tractor's "TST-1" diagnostic mode (if equipped) to observe live sensor readings. When the shuttle lever is in neutral, the main and sub sensor voltages (often labeled T12 and T13) should read approximately 2.2 volts and 2.74 volts, respectively.

3. 3

   Inspect the wiring harness for disconnections or short circuits. The service manual notes that this code can be triggered by a short-circuited solenoid ON/OFF valve or a disconnection in the solenoid proportional reducing valves (main shift L and H).

1. 1

   Prepare tractor for service

   Park the tractor on a level surface, turn off the engine, and engage the parking brake.

2. 2

   Locate components

   Locate the shuttle switch/sensor on the steering column/dash area and the hydraulic shuttle valve assembly on the transmission housing.

3. 3

   Inspect wiring harness

   Inspect the physical wiring harness leading to the shuttle sensor and the shuttle valve solenoids for chafing, corrosion, or loose pins.

4. 4

   Evaluate shuttle switch/sensor

   If the wiring is intact but the sensor voltages are out of specification (not reading ~2.2V and ~2.74V in neutral), the shuttle switch/sensor has failed and must be replaced.

5. 5

   Evaluate hydraulic shuttle valve assembly

   If the sensor is functioning correctly but the tractor still will not drive and throws phase/signal codes, the issue may be a mechanical or electrical failure within the hydraulic shuttle valve assembly itself.

6. 6

   Replace faulty component

   Replace the faulty component (sensor or valve assembly).

7. 7

   Clear codes and test

   Clear the error codes using Kubota's Diagmaster software (or by cycling the battery/system if applicable) and test drive the tractor to ensure smooth shifting between forward and reverse.