# Service bulletin LI49.20\-N\-076565

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

- Type: Service bulletin
- NHTSA id: 11021170
- Published by NHTSA: 2025\-08\-01
- Manufacturer's number: LI49.20\-N\-076565
- Manufacturer's date: 2025\-07\-23
- NHTSA component: UNKNOWN OR OTHER

## NHTSA's summary

Check engine light with fault code P300E3B in the CDI control unit CDI \(N3/28\) Complaint Check engine light is illuminated with fault code P300E3B “The efficiency of component 'SCR catalytic converter' is not sufficient" stored in the CDI control unit \(N3/28\). 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: N3/28 – Motor Electronics 'CDI61NFZ' for combustion engine 'OM642' \(CDI\):

## The document

- [NHTSA's copy of the document (PDF)](https://static.nhtsa.gov/odi/tsbs/2025/MC-11021170-0001.pdf)
- [If that address does not open, try this one](https://static.nhtsa.gov/odi/tsbs/2025/MC-11021170-9999.pdf)

The document is the manufacturer's. This site does not hold it.

## Trouble codes named

P300E

## Vehicles listed

- 2019 to 2020 FREIGHTLINER SPRINTER \(VS30\)
- 2021 FREIGHTLINER SPRINTER 1500
- 2021 FREIGHTLINER SPRINTER 2500
- 2021 FREIGHTLINER SPRINTER 3500
- 2021 FREIGHTLINER SPRINTER 4500
- 2019 to 2020 MERCEDES\-BENZ SPRINTER \(VS30\)
- 2021 MERCEDES\-BENZ SPRINTER 1500
- 2021 MERCEDES\-BENZ SPRINTER 2500
- 2021 MERCEDES\-BENZ SPRINTER 3500
- 2021 MERCEDES\-BENZ SPRINTER 4500

JSON: [/v1/bulletins/11021170](/v1/bulletins/11021170)

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