John Deere 1079 – CAB/ACU: Sensor Supply 1 Voltage Fault

The Cab Control Unit (CAB) or Armrest Control Unit (ACU) has detected an issue with the voltage on the Sensor Supply 1 circuit. This circuit provides a regulated 5-volt reference signal to a group of sensors. The fault is triggered when the voltage deviates from its specified range (typically 4.8 to 5.2 volts), indicating a problem with the power source, the circuit providing power, or a shorted sensor pulling down the reference voltage.

• 7185J
• 7195J
• 7205J
• 7210J
• 7225J
• 8130
• 8230
• 8330
• 8430
• 8530
• 7720
• 7820
• 7920
• 9230
• 9330
• 9430
• 9530
• 9630

1. 1

   Check battery and chassis ground connections to ensure they are fully charged, clean, tight, and free of corrosion.

2. 2

   Inspect fuses related to the CAB or ACU controllers (e.g., fuse F22 for the ACU).

3. 3

   Visually inspect the wiring harnesses connected to the sensors on the Sensor Supply 1 circuit for chafing, pinching, or rodent damage.

4. 4

   Disconnect and inspect the connectors for the implicated sensors and the associated control unit (CAB or ACU) for dirty, damaged, or corroded pins.

1. 1

   Identify sensors on the circuit

   Determine which sensors are on the Sensor Supply 1 circuit for your specific model. Common sensors include the Foot Throttle Sensor, Clutch Pedal Sensor, Active Seat Position Sensor, and Active Seat Accelerometer Sensor.

2. 2

   Isolate the faulty component

   Turn the keyswitch to the OFF position. Disconnect all sensors that are part of the Sensor Supply 1 circuit. Turn the keyswitch ON. If the fault code 1079 is no longer active, one of the disconnected sensors or its wiring is the cause. If the code remains active, there is likely a short in the main wiring harness or an issue with the control unit itself.

3. 3

   Identify the specific faulty sensor

   With the keyswitch OFF, reconnect one sensor at a time. Turn the keyswitch ON after each connection to see if the fault code reappears. The sensor that causes the fault code to return upon being reconnected is the likely source of the problem.

4. 4

   Test the suspect sensor and wiring

   Disconnect the identified suspect sensor again. With the keyswitch ON, use a multimeter to check for a 5-volt supply and a good ground at the sensor's connector on the harness side. If the 5-volt supply or ground is missing, repair the wiring between the control unit and the sensor. If the 5-volt supply and ground are good at the connector, replace the faulty sensor.