John Deere 1493 – Cornerpost Control Unit: Missing Master Tailings Sensor CAN Message

The Cornerpost Control Unit is not receiving the expected CAN bus data message regarding tailings volume from the Master Tailings Sensor. This indicates a communication interruption in the data link between the sensor and the control module, preventing the system from monitoring the volume of material in the tailings elevator.

• CTS Combines (from serial number 070231)
• 9450
• 9540
• 9550
• 9560
• 9580
• 9640
• 9650
• 9660
• 9670
• 9680
• 9560 STS
• 9650 STS
• 9660 STS
• 9670 STS
• 9750 STS
• 9760 STS
• 9770 STS
• 9860 STS
• 9880 STS
• 9540 WTS
• 9560 WTS
• 9580 WTS
• 9640 WTS
• 9660 WTS
• 9680 WTS
• T550
• T560
• T660
• T670
• W540
• W550
• W650
• W660
• C670

1. 1

   Visually inspect the wiring harness and connectors between the Master Tailings Sensor and the main vehicle harness for chafing, corrosion, or loose connections.

2. 2

   Inspect the Master Tailings Sensor lens for dirt, material coating, or dust behind the seal (especially if the display shows consistently full or empty readings).

3. 3

   Perform an operational check after cleaning: with the separator engaged at high idle for two minutes and the header disengaged, verify if the tailings volume graph zeroes out.

4. 4

   Perform a CAN bus resistance check at the diagnostic connector between the CAN High and CAN Low pins (often pins C and D) with the battery disconnected. A healthy bus reads approximately 60 Ohms. 120 Ohms suggests a missing terminating resistor or open circuit, while significantly lower indicates a short circuit.

5. 5

   Perform a CAN bus voltage check with the battery reconnected and key ON (without starting the engine). Measure DC voltage to a good chassis ground: CAN High should be 2.5-3.5 Volts, CAN Low should be 1.5-2.5 Volts. Outside these ranges indicates a short to power/ground or faulty controller.

6. 6

   Perform a sensor transceiver resistance check with the sensor disconnected (resistance from CAN High to Ground and CAN Low to Ground should be very high/open circuit).

1. 1

   Address visual and physical issues

   Clean dirty sensor lenses, repair any damaged wiring or connectors found during inspection, and ensure all connectors are seated firmly. Apply dielectric grease to prevent moisture intrusion.

2. 2

   Perform CAN bus electrical tests

   Carry out the resistance (60 Ohms expected) and voltage (CAN High 2.5-3.5V, CAN Low 1.5-2.5V) checks to determine if the issue lies within the general CAN bus wiring or is specific to the sensor.

3. 3

   Isolate the faulty component

   If the main CAN bus checks out with correct resistance and voltages, focus troubleshooting on the Master Tailings Sensor itself or its specific branch of the harness.

4. 4

   Test the sensor transceiver

   Measure resistance from the CAN High pin to the Ground pin, and CAN Low to Ground on the sensor connector. If the internal resistance is low, the sensor's transceiver is damaged.

5. 5

   Replace the Master Tailings Sensor

   If diagnostic checks point to a sensor failure, replace it. If the fault code persists after replacement, the issue may lie in the wiring harness between the sensor and the Cornerpost Control Unit, or the control unit itself. In such cases, consulting a John Deere dealer is recommended.