John Deere 1388 – E04 Control Unit (Left Control Unit 2): Rotor Drive Pressure Voltage Too Low

The voltage from the Rotor Drive Pressure sensor is below the acceptable threshold, measuring less than 0.20 VDC. This indicates a potential issue with the electrical signal related to the rotor drive's hydraulic pressure. The system expects a certain voltage range to correspond with the operational pressure; when the voltage drops below 0.20 VDC, the control unit interprets this as a fault condition.

• 9470 STS
• 9560 STS
• 9570 STS
• 9650 STS
• 9660 STS
• 9750 STS
• 9760 STS
• 9770 STS
• 9860 STS
• 9870 STS
• 9070 STS
• S600
• S670
• S670HM
• S680HM
• S760
• S770
• S780
• S785
• S790

1. 1

   Carefully inspect the wiring harness and connectors associated with the Rotor Drive Pressure Sensor (cc# 723) for any signs of damage, such as chafing, corrosion, or loose connections

2. 2

   Check for an open circuit, a short to ground in the signal wire, or a faulty sensor

3. 3

   Ensure the sensor is receiving the correct supply voltage. A loss of power to the sensor would result in a low voltage signal

1. 1

   Gain Access to the Sensor

   Locate the Rotor Drive Pressure Sensor (cc# 723) on the rotor drive hydraulic system.

2. 2

   Test the Sensor

   Disconnect the sensor's electrical connector. Using a multimeter, check for the specified supply voltage at the connector's power pin. With the sensor reconnected and the machine in the appropriate state (consult the technical manual), measure the signal voltage from the sensor. A reading below 0.20 VDC would confirm the fault condition.

3. 3

   Test the Wiring

   If the supply voltage is absent, trace the wiring back to the E04 control unit to identify and repair any breaks or shorts. If the supply voltage is present but the signal is low, test the signal wire for continuity and for any shorts to ground between the sensor and the control unit.

4. 4

   Replace the Sensor

   If the wiring is intact and the sensor is receiving power but still outputting a low voltage, the sensor itself is likely faulty and should be replaced.