John Deere 4364.18 – Engine Control Unit (ECU) / Engine Control Module (ECM): Catalytic Converter Efficiency of SCR System Moderately Low

The NOx sensor downstream of the Selective Catalytic Reduction (SCR) catalyst detects that the system is not converting enough NOx. The NOx value at the outlet of the SCR system is too high to start or maintain proper regeneration. This triggers an engine derate (power limitation) to comply with emissions standards.

• 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
• 8245R
• 8400R
• 8R 410
• 9R series
• 9RT series
• 9470RT
• 9520RT
• 9570RT
• 6105M
• S-Series
• S680
• S780
• T550
• 8000 series forage harvesters
• 9000 series forage harvesters
• 350G LC

1. 1

   Check for Accompanying Codes: Address any active DEF system codes first (e.g., DEF dosing system, DEF pump pressure, DPF soot load).

2. 2

   Verify DEF Quality: Ensure the DEF is fresh and tests at the correct concentration (approx. 32.5%). Contaminated or degraded fluid is the leading cause of this code.

3. 3

   Inspect the DEF Dosing Unit/Injector: Check the DEF injector nozzle and the SCR mixing chamber for severe urea crystallization/clogging.

4. 4

   Check NOx Sensors: Look for a biased or drifting outlet NOx sensor that will falsely report poor conversion efficiency.

5. 5

   Check for Software Updates: Verify if ECU calibration updates (e.g., SW63154C, SW62554F, SW62275H) are needed to prevent incorrect setting of DTCs during high idle or low SCR temperature conditions.

1. 1

   Connect Diagnostic Tool

   Hook up John Deere Service Advisor (or an equivalent heavy-duty scanner like Jaltest) to read all active and stored codes.

2. 2

   Update ECU Software

   If the machine is running older software, flash the ECU with the latest calibration to rule out false triggers caused by low SCR temperatures.

3. 3

   Address DEF Fluid

   If DEF quality is suspect, drain the DEF tank completely, flush it, and refill it with fresh, certified Diesel Exhaust Fluid.

4. 4

   Clean/Replace Dosing Components

   Remove the DEF dosing injection nozzle. If it is heavily crystallized or fails a dosing quantity test via the diagnostic tool, clean it or replace the dosing unit pump/nozzle.

5. 5

   Replace NOx Sensor(s)

   If the DEF system is dosing correctly but the outlet NOx readings are erratic or drifting, replace the downstream NOx sensor.

6. 6

   Perform SCR Verification Check

   Once repairs are made, use the diagnostic tool to initiate an 'SCR system verification check' (similar to a parked regeneration). This tests the SCR catalytic converter's efficiency under controlled, high-temperature conditions.

7. 7

   Replace SCR Catalyst (Worst Case)

   If the verification check fails after confirming DEF quality, dosing volume, and NOx sensor accuracy, the SCR catalyst itself is degraded and must be replaced.