New Holland 3226 – ECM: Aftertreatment Outlet NOx Sensor Fault

This fault code indicates a problem with the Aftertreatment 1 Outlet NOx Sensor, which is located in the exhaust system after the Selective Catalytic Reduction (SCR) catalyst. The sensor measures the concentration of nitrogen oxides in the treated exhaust gas to verify SCR efficiency. When this fault is active, the Engine Control Module (ECM) detects erratic, out-of-calibration, or missing data from the sensor, which may illuminate a warning light and cause the engine to derate (reduce power) to limit emissions.

• T5.100
• T6.120
• T8.380
• T8.410
• T9.480
• T9.700
• CR8.90
• CR10.90
• CX8.80
• CX8.90
• B110C
• C238

1. 1

   Retrieve the full fault code list using a diagnostic tool to check for related SCR codes (e.g., SPN 3216 for inlet NOx or SPN 4364 for low SCR efficiency).

2. 2

   Visually inspect the entire exhaust system for leaks between the SCR catalyst and the outlet NOx sensor (look for soot trails at clamps or joints).

3. 3

   Inspect the outlet NOx sensor wiring harness and connectors for chafing, heat damage, corrosion, or loose pins.

4. 4

   Test the Diesel Exhaust Fluid (DEF) quality using a refractometer (urea concentration should be approximately 32.5%).

5. 5

   Remove and inspect the DEF doser and exhaust mixing chamber for heavy white crystal formations that could block exhaust flow.

6. 6

   Perform live data analysis with a diagnostic tool at operating temperature: compare inlet vs. outlet NOx readings and wiggle-test the sensor harness to check for erratic signals.

1. 1

   Address foundational issues

   Repair any identified exhaust leaks, wiring/connector problems, or DEF system issues (crystallization, poor quality fluid). Clear the codes and operate the machine to see if the fault returns before condemning the sensor.

2. 2

   Remove outlet NOx sensor

   If no other issues are found, allow the exhaust system to cool completely. Disconnect the sensor's electrical connector and use a 22mm socket to carefully unscrew the sensor from the exhaust pipe after the SCR catalyst. Inspect the sensor tip for contamination (soot, deposits); while cleaning is sometimes possible, replacement is often more reliable.

3. 3

   Install new NOx sensor

   Install the replacement NOx sensor and tighten it to the manufacturer's specified torque (typically 40-50 Nm). Securely reconnect the electrical connector.

4. 4

   Clear codes and verify repair

   Use a diagnostic tool to clear the fault code. Start the machine and bring it up to operating temperature to allow the new sensor's internal heater to activate. Perform a test drive or run the machine under load to verify the repair.