4D16

4D16 - P20EE

Information saved in
DDE

Fault code
4D16 - P20EE

Fault text
SCR system, efficiency: Efficiency too low

Fault description
Monitoring of NOx efficiency level (entire efficiency
range). The monitoring function links SCR efficiency level
monitoring in efficiency range 1 and efficiency range 2.
The diagnostic trouble code is logged when an error is
detected during monitoring of one of the two ranges.

Condition for fault identification
Test condition:
The monitoring function is active when the conditions for
SCR efficiency monitoring in efficiency range 1 and
efficiency range 2 (according to temperature range) are
satisfied.
Voltage condition:
The monitoring function is active when the conditions for
SCR efficiency monitoring in efficiency range 1 and
efficiency range 2 (according to temperature range) are
satisfied.

Condition for fault memory entry
Event debounced (4)

Action in service
1. Refill SCR system tank with new fluid (urea quality)
2. Use diagnostic system to test SCR converter.
4. Check metering valve.
5. Check NOx sensors.
6. Inspect metering module for correct installation position
and contamination.
If results of all tests are OK:
Replace SCR converter.

Fault effect and breakdown warning
-

Driver information
Warning light:
MIL

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.