John Deere 004364.18 – ECU: SCR After Treatment Not Working Properly

The Selective Catalytic Reduction (SCR) after-treatment system's efficiency is below the required threshold. The Engine Control Unit (ECU) monitors exhaust gases using upstream and downstream NOx sensors. When the downstream sensor detects a higher than expected level of NOx, it triggers this code, indicating the chemical reaction to neutralize harmful emissions is failing. This condition affects emissions control and can cause the engine to derate, limiting its power.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R

1. 1

   Check Diesel Exhaust Fluid (DEF) quality: Visually inspect for clarity and a faint ammonia smell. Use a refractometer (such as John Deere JDG11594 or JDG11684) to verify urea concentration is between 31.8% and 33.2%.

2. 2

   Inspect the DEF system: Check for leaks, kinks, or damage in lines and hoses, and visually inspect the DEF injector for crystallization or buildup.

3. 3

   Check for exhaust leaks: Inspect the exhaust system between the engine and the SCR catalyst, as leaks can alter NOx sensor readings.

4. 4

   Access and record all fault codes: Use onboard diagnostics to check for other active or stored codes related to NOx sensors, DEF pumps, or temperature sensors to pinpoint the root cause.

1. 1

   Clean or test the DEF injector

   Clean any crystal buildup on the injector. Perform a DEF injector quantity test using a diagnostic scan tool (expected volume is typically 40-55ml over a 2-minute test). Replace the injector if flow is incorrect.

2. 2

   Test the NOx sensors

   Inspect wiring and connectors for the upstream and downstream NOx sensors for damage, corrosion, or loose connections. Monitor live data with a diagnostic tool for erratic or out-of-range readings. Replace faulty sensors.

3. 3

   Perform a stationary (parked) regeneration

   Perform a parked regeneration to clear excess soot from the Diesel Particulate Filter (DPF), as a clogged DPF can sometimes trigger SCR faults.

4. 4

   Clear fault codes and perform a drive cycle

   Clear the fault codes using a diagnostic tool and operate the machine under normal load to allow the ECU to verify the repair was successful.