John Deere 3226.12 – ECU: Aftertreatment Outlet NOx Sensor Faulty / Data Inaccurate

This code indicates that the aftertreatment outlet NOx sensor is unable to accurately measure the nitrogen oxide (NOx) levels in the exhaust gases after they have passed through the Selective Catalytic Reduction (SCR) emission control system. The sensor performs its own internal diagnostics and reports the malfunction back to the primary controller via the J1939 data link. When this code is active, the ECU may limit engine power, deactivate the SCR system, or enter a fault state to mitigate the impact of the incorrect readings.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6R Series
• 7R Series
• 8R Series
• 8RT Series
• 9R Series
• 9RT Series
• 9RX Series
• 9470RT
• 9520RT
• 9570RT
• 7210R
• 8320RT
• 337E
• 437E
• 544K
• 644K
• 1050K
• 210G
• 210GLC
• R4038
• R4044
• R4045
• S-Series
• T-Series
• W-Series
• X9

1. 1

   Examine the outlet NOx sensor, its control module, and the wiring harness for signs of physical damage, wear, or heavy soot accumulation that might interfere with its function.

2. 2

   Verify the integrity of the CAN bus circuit by checking the resistance at the unit; a reading of 60 ohms indicates that the termination resistors are good.

3. 3

   Use a diagnostic tool (such as John Deere Service ADVISOR) to monitor the sensor's live NOx readings and compare them against expected values under similar operating conditions to confirm the inaccuracy.

1. 1

   Power Down

   Turn the ignition OFF and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the aftertreatment outlet NOx sensor. It is mounted on the exhaust pipe downstream of the SCR catalytic converter.

3. 3

   Removal

   Disconnect the electrical connector from the NOx sensor module. Carefully unthread the sensor probe from the exhaust pipe.

4. 4

   Installation

   Thread the new NOx sensor into the exhaust pipe and tighten to OEM specifications. Mount the attached control module and plug in the electrical connector.

5. 5

   Reset and Clear

   Reconnect the battery. Connect your diagnostic tool, clear the 003226.12 fault code, and reset the ECU to clear any derate or error states.

6. 6

   Verification

   Conduct a test run under various operational conditions (or perform a forced regeneration) to ensure the new sensor provides accurate readings and the code does not return.