P20EE/008430

Possible Symptoms

• MIL (Malfunction Indicator Lamp) ON
• Loss of power (limp mode) possible
• Increased emissions
• DTC stored in ECM

Possible Causes

• SCR NOx Catalyst efficiency below threshold
• Faulty NOx sensor(s) (upstream or downstream)
• Faulty Reducing Agent Injector -N474-
• Reducing Agent (AdBlue®) quality concern
• Incorrect dosing of reducing agent
• Exhaust leaks upstream of SCR Catalyst
• Catalyst temperature not within range
• DPF regeneration status interfering with monitoring

Possible Solutions

• If a NOx sensor DTC is also present, diagnose that DTC first
• Check Reducing Agent (AdBlue®) quality
• Check NOx Sensor Control Modules
• Check Reducing Agent Injector -N474- https://forums.ross-tech.com/index.php?threads/18568/
• Inspect for exhaust leaks before SCR catalyst
• Verify AdBlue system operation and dosing
• Perform basic settings / adaptations as per factory repair manual
• Replace SCR catalyst if efficiency cannot be restored

Special Notes

• Criteria for Monitoring (as per the offical rapair manuals)
  • Difference between calculated and measured efficiency > 0.3 [-]
  • Status NOx sensor downstream = ready
  • Status NOx sensor upstream = ready
  • Urea dosing = active
  • Adaptation = not active
  • DPF regeneration = not active
  • SCR Catalyst temp gradient < 0.2 – 0.34 K/s
  • SCR catalyst modeled temp = 240 – 350 °C
  • NOx concentration upstream < 1,500 ppm
  • Integrated NOx mass flow upstream ≥ 0.4 g
• If AdBlue® is contaminated or incorrect concentration, system performance may be affected. Always use fresh, correct specification AdBlue®.
• If conditions for monitoring are not met (temperature, regeneration status, etc.), efficiency check may not run.