P122D

4749 - P122D

Information saved in
DDE

Fault code
4749 - P122D

Fault text
DDE: Nitrogen oxide sensor downstream of SCR catalytic
converter, line disconnection short circuit to ground: Short-
circuit

Fault description
The error is recognized when NOx sensor 2 (behind SCR
converter) transmits a short circuit error (linear, binary
lambda value, NOx signal or heater circuit) on the CAN.
This is the case when at least one of the following error
conditions has been recognized:
- NOx sensor short circuit == 1
- Linear lambda short circuit == 1
- Binary lambda short circuit == 1
- Short circuit in heater == 1

Condition for fault identification
Test condition:
The following conditions must be satisfied before the NOx
sensor diagnosis function is enabled == 1
- Heater diagnosis enabled == 1
- NOx sensor heater temperature has reached specified
temperature. == 1
- No electrical malfunctions have been detected is locked.
Voltage condition:
The following conditions must be satisfied before the NOx
sensor diagnosis function is enabled == 1
- Heater diagnosis enabled == 1
- NOx sensor heater temperature has reached specified
temperature. == 1
- No electrical malfunctions have been detected is locked.

Condition for fault memory entry
Debounce (2000 ms)

Action in service
1. Check wiring and plug-in connections (power supply to
NOx sensor control module and NOx sensor).
2. Replace NOx sensor 2 (behind SCR converter).

Fault effect and breakdown warning
-

Driver information
Warning light:
MIL

Service instruction
none