Massey Ferguson 003218.14 – ECU: Supply Voltage Issue To Upstream NOx Sensor

The engine control unit has detected an abnormal voltage supply to the NOx sensor located upstream of the Diesel Oxidation Catalyst (DOC). This disruption prevents the sensor from heating to its operational temperature or sending accurate NOx concentration signals to the ECU. Consequently, this can lead to incorrect DEF dosing, increased emissions, check engine light activation, and potentially force the engine into a derated 'limp mode' with a noticeable loss of power.

• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710SL
• 5711SL
• 5712SL
• 5713SL
• 6711
• 6712
• 6712S
• 6714S
• 6715S
• 6716S
• 6718S
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S

1. 1

   Connect a diagnostic scan tool to confirm 003218.14 is active, check for other after-treatment codes, and monitor live NOx sensor voltage and ppm data.

2. 2

   Visually inspect the upstream NOx sensor and its wiring harness for physical damage, connector pin corrosion, or chafing/melting against hot exhaust components.

3. 3

   With ignition on, use a multimeter to verify correct battery voltage and a solid ground connection at the NOx sensor's electrical connector.

4. 4

   Disconnect the sensor and check continuity and resistance in the wiring harness between the sensor connector and the ECU (resistance above 0.5 ohms on a signal wire indicates a wiring fault).

5. 5

   With the sensor disconnected and at ambient temperature, measure resistance across the heater circuit pins on the sensor (typical resistance is 2 to 6 ohms; readings outside this indicate internal heater failure).

1. 1

   Safety First

   Ensure the tractor is parked on a level surface, the engine is off, and the exhaust system is completely cool to prevent burns.

2. 2

   Locate the Sensor

   Identify the upstream NOx sensor, which is threaded into the exhaust pipe before the Diesel Oxidation Catalyst (DOC).

3. 3

   Disconnect Electrically

   Carefully disconnect the wiring harness from the NOx sensor module.

4. 4

   Remove the Sensor

   Using the appropriate size wrench, carefully unscrew the NOx sensor from the exhaust pipe. If the sensor is seized, apply a penetrating lubricant and allow it to soak before attempting removal again to avoid damaging the threads in the exhaust pipe.

5. 5

   Prepare for Installation

   Apply a small amount of ceramic-based anti-seize compound to the threads of the new sensor, being careful not to get any on the sensor's tip.

6. 6

   Install the New Sensor

   Thread the new NOx sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect and Secure

   Reconnect the wiring harness to the new sensor module and ensure it is securely fastened away from any hot exhaust components.

8. 8

   Clear Fault Codes

   Use a diagnostic scan tool to clear the 003218.14 fault code and any other related inactive codes from the ECU.

9. 9

   Perform Relearn/Calibration

   Some systems may require a NOx sensor relearn or adaptation procedure to be performed with the scan tool to ensure the ECU recognizes the new sensor. Start the engine and allow it to reach operating temperature to verify that the fault does not return.