4D17

4D17 - P20EE

Information saved in
DDE

Fault code
4D17 - P20EE

Fault text
SCR system, efficiency: Efficiency too low in user 1 (level
control)

Fault description
Monitoring of NOx efficiency level. The diagnostic trouble
code is logged when the average NOx conversion efficiency
of the SCR system falls below the minimum NOx efficiency
level threshold (varies according to operating point).
The efficiency level is calculated based on the mass flow
rates of NOx upstream and downstream from the SCR
converter and the correction factor SCRChk_facEta1Cor_C.
The efficiency level threshold is calculated based on the
mass flow rate of the NOx upstream and downstream from
the SCR converter and a threshold value.

Condition for fault identification
Test condition:
The test routine runs when the following conditions are
satisfied:
- The efficiency level threshold is greater than 0.
- A new valid NOx efficiency level has been calculated
(operating point and monitored value are plausible and
valid).
The error check runs continuously during the calculation of
efficiency level, provided that it supplies a valid, plausible
value, in a grid with a 100 ms periodicity.
Voltage condition:
The test routine runs when the following conditions are
satisfied:
- The efficiency level threshold is greater than 0.
- A new valid NOx efficiency level has been calculated
(operating point and monitored value are plausible and
valid).
The error check runs continuously during the calculation of
efficiency level, provided that it supplies a valid, plausible
value, in a grid with a 100 ms periodicity.

Condition for fault memory entry
Event debounced (4)

Action in service
1. Refill tank with new fluid (urea quality)
2. Use diagnostic system to test SCR converter.
3. Check metering valve.
4. Check NOx sensors.
5. Replace SCR converter

Fault effect and breakdown warning
-

Driver information
Warning light:
KEINE

Service instruction
- Urea quality (quality determination): Extract contents from
tank and then refill.
- NOx sensor before or behind SCR converter (indentified
by corresponding diagnostic trouble code entry in ECU error
memory) furnishing implausible data
- Defective SCR converter, check with SCR converter
system test
- Coating on diesel particulate filter (indicated by DTC
4B91)
- Check operation of metering valve.