Manufacturer Code Charts: 148800

There is an internal fault in component NOx sensor downstream of SCR catalytic converter.


Possible cause:

- NOx sensor downstream of SCR catalytic converter
Affected functions:

- Power generation

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Test 1: Check component NOx sensor downstream of SCR catalytic converter.

1. Check component NOx sensor downstream of SCR catalytic converter.

Test 1.1: Check power supply of component NOx sensor downstream of SCR catalytic converter.

Test 1.2: Inspect CAN link between component NOx sensor downstream of SCR catalytic converter and component N3/9 (CDI control unit).

1.1. Check power supply of component NOx sensor downstream of SCR catalytic converter.
Figure legend

- N37/8 (NOx control unit downstream of SCR catalytic converter)
- N37/8b1(NOx sensor downstream of SCR catalytic converter)
Test prerequisite

- Battery voltage is OK.
- The fuses are OK.
Test sequence

- Switch off ignition.
- Disconnect connector at component N37/8 (NOx control unit downstream of SCR catalytic converter).
- Measure direct voltage with multimeter between sockets (N37/8x1) 2 and (N37/8x1) 1
- Measure direct voltage with multimeter between sockets (N37/8x1) 5 and (N37/8x1) 1
- Switch on ignition.
Specified value

- Voltage [11.0...15.0] V
Question

- Is the measurement value OK?







YES
The measurement value is OK.End of test

NO
The measurement value is not OK.Possible cause and remedy

- F58f104 (Fuse 104)
- Line from component N37/8 (NOx control unit downstream of SCR catalytic converter) to component F58 (Engine compartment fuse and relay box)
End of test

1.2. Inspect CAN link between component NOx sensor downstream of SCR catalytic converter and component N3/9 (CDI control unit).
If several fault codes regarding CAN communication have occurred, the following causes of the fault are likely

- Short circuit or open circuit of CAN wires
- Voltage supply of component NOx sensor downstream of SCR catalytic converter
Figure legend

- N37/8 (NOx control unit downstream of SCR catalytic converter)
- N37/8b1(NOx sensor downstream of SCR catalytic converter)
Test sequence

- Switch off ignition.
- Detach coupling at component N37/8 (NOx control unit downstream of SCR catalytic converter).
- Detach coupling at component N37/7 (NOx control unit downstream of diesel particulate filter).
- Measure resistance with multimeter between sockets (N37/8x1) 3 and (N37/8x1) 4
Specified value

- Resistor[55...65]ohms
Question

- Is the measurement value OK?







YES
The measurement value is OK.End of test

NO
The measurement value is not OK.Possible cause and remedy

- Check lines and connectors between components N37/8 (NOx control unit downstream of SCR catalytic converter) and N3/9 (CDI control unit) for short and open circuit.
End of test