FREIGHTLINER, MERCEDES-BENZ

LI49.20-N-079593

2025-07-25 · NHTSA 11021173

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영어 원문

Check engine light with fault code P20EEFE in the CDI control unit CDI (N3/47) Complaint Check engine light is illuminated with fault code P20EEFE "The efficiency of component 'SCR catalytic converter' is not sufficient" stored in the CDI control unit (N3/47). Cause Excessive ammonia slip is being detected in the SCR system, often triggered by IUMPR (In-Use Monitor Performance Ratio) thresholds. This typically indicates that the SCR catalyst is not converting DEF (AdBlue) efficiently under moni- tored conditions. Common Driving Scenario: •Non-dynamic driving (e.g., highway cruising with cruise control set) •Minimal load changes, steady-state exhaust flow Contributing Factors: •Software influence – IUMPR (In-Use Monitor Performance Ratio) thresholds •DEF Overdosing – Over-injection due to faulty NOx sensors, dosing valve issues, or poor DEF quality •Low Exhaust or Catalyst Temperatures – Common under low-load conditions; reduces SCR conversion efficiency •Catalyst Degradation or Contamination – Aging catalyst or contamination from oil, coolant, or poor-quality DEF Remedy IMPORTANT: Do not replace any components unless instructed through TIPS. For Model Year 2019–2021 Vehicles: •Update the following control units to the latest available software: N3/47 - Motor electronics 'CDI43' for combustion engine 'OM651' (CDI) N118/5 - Selective catalytic reduction (SCR GEN3) •If no newer software is available, proceed with the inspection and documentation steps listed under the No Newer Software section. •Once all inspections are complete, open a TIPS case directed to the Powertrain Inbox, referencing this LI with the collected information and data. No Newer Software Vehicles: Perform the following steps in order. Document all findings with photos and actual values where applicable: 1. Tailpipe Wipe Test •Perform and photograph results. 2. NOx Sensor Harness Inspection •Check connectors, pins, crimps, and harnesses 3. Sensor Plausibility Checks •Record actual values for all pressure and temperature sensors: •Once with the engine cold (≥8 hours off) •Again, at full operating temp, engine idling 4. Smoke Test – Intake, Charge Air, Exhaust •Apply ≤26 psi from the tailpipe. •Seal at clean air line. •Manipulate components during the test. •Document any leaks. 5. DPF Data •Record actual values and regeneration history. 6. SCR Temp Sensor Wiring •Inspect wiring and pins. •Confirm sensor reaches operating temp while driving. •Document time to temp. 7. AdBlue Injector Inspection •Check for clogging or leaks. •Photograph nozzle(s). 8. AdBlue Pressure Test •Remove injector(s), perform 2–3 pressure tests. •Check for leaks and document with photos. 9. DEF Quality Check •Collect a sample. •Note color, clarity, separation, odor, and quantity. •Photograph the fluid and spray pattern. 10. DPF & SCR Visual Inspection •Separate exhaust downstream of DPF. •Inspect for soot, blockage, or damage. •Photograph findings. 11. SCR Catalyst Interior •Inspect for dried AdBlue residue. •Photograph the interior. 12. NOx Sensor Graphing •Perform multiple test drives at varying speeds. •Capture 3–4 graphs/screenshots of NOx sensor signals using XENTRY. •Include one at idle, engine warm. •Disconnect AdBlue valve, drive 30 min, capture 2–3 more graphs. •Once all inspections are complete, open a TIPS case directed to the Powertrain Inbox, referencing this LI with the collected information and data.

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