Massey Ferguson 3225.05 – Engine Control Unit (ECU): NOx Sensor Before DOC Signal Issue

This code indicates a signal failure from the upstream Nitrogen Oxide (NOx) sensor, which is located in the exhaust system before the Diesel Oxidation Catalyst (DOC). The ".05" suffix in the J1939 standard typically denotes "Current Below Normal or Open Circuit," meaning the controller has detected a broken wire, an unplugged connector, or an internal open circuit within the sensor itself.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7714 to 7726S

1. 1

   Visually inspect the NOx sensor wiring harness for chafing, melting from exhaust heat, or rodent damage

2. 2

   Disconnect the NOx sensor module connector and check for pushed-out pins, water intrusion, or corrosion

3. 3

   Turn the key to the ON position and verify that the sensor is receiving proper supply voltage (12V or 24V) and has a solid ground

4. 4

   Check the CAN High and CAN Low pins at the sensor connector for proper resistance (typically 60 ohms across the network) and voltage

5. 5

   Ensure there are no exhaust leaks between the engine manifold and the DOC

1. 1

   Preparation

   Turn off the tractor, remove the key, and disconnect the negative battery cable. Allow the exhaust system to cool completely.

2. 2

   Disconnect

   Unplug the electrical connector for the upstream NOx sensor. Unclip the wiring harness from any retaining brackets.

3. 3

   Removal

   Using a specialized NOx/O2 sensor socket (usually 22mm or 7/8"), carefully unscrew the sensor from the exhaust pipe before the DOC. Tip: If the sensor is seized, apply penetrating oil and allow it to soak.

4. 4

   Installation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (avoid getting any on the sensor probe itself, as this will ruin it). Thread the sensor in by hand to prevent cross-threading, then tighten to the OEM torque specification.

5. 5

   Routing

   Route the new sensor's wiring harness exactly as the old one was routed, ensuring it is secured away from direct heat sources and moving parts. Reconnect the electrical plug.

6. 6

   Relearn/Clear

   Reconnect the battery. Use an AGCO/Massey Ferguson compatible diagnostic scan tool to clear the 003225.05 fault code. Perform a stationary forced regeneration or a test drive under load to verify the sensor is reading correctly and the code does not return.