John Deere HMM3510 – HMM: Mass Flow Sensor Voltage Out of Range

The HMM (Moisture Sensor) control unit has detected that the electrical voltage supplied to the mass flow sensor on circuit CC971 is outside of its normal operating range (greater than 5.35 volts or less than 4.65 volts). This Service Alert disables the mass flow function and must be addressed promptly to prevent the issue from escalating to a severe STOP indicator.

• 9670 STS
• 9770 STS
• 9000 Series
• S-Series
• T-Series
• W-Series

1. 1

   Restart the machine to verify if the fault code clears or if it is a persistent active fault.

2. 2

   Inspect the mass flow sensor's impact plate in the clean grain elevator for caked-on dirt, mud, debris, or physical damage. Clean if necessary.

3. 3

   Inspect the wiring harness and connectors between the HMM control unit and the mass flow sensor for damage, corrosion, or loose connections, specifically on circuits CC970, CC971, and CC972.

4. 4

   Using a multimeter, back-probe the mass flow sensor connector to measure the voltage on the power supply wire (circuit CC971). The expected voltage is approximately 5V. A reading above 5.35V or below 4.65V confirms the fault condition.

1. 1

   Repair wiring harness

   If diagnostic checks reveal a short to power, short to ground, or an open circuit on the sensor wiring, repair or replace the damaged section of the wiring harness.

2. 2

   Replace mass flow sensor

   If the wiring is intact and the voltage supply from the HMM controller is confirmed to be out of specification, replace the mass flow sensor.

3. 3

   Replace HMM control unit

   If replacing the mass flow sensor does not resolve the voltage issue, the HMM control unit itself may be faulty. Replace the HMM control unit.

4. 4

   Perform system calibration

   After replacing either the mass flow sensor or the HMM control unit, perform a calibration of the moisture and yield systems to ensure accurate readings.