Service information: Notes on damage codes and fault codes for on-board diagnosis (OBD) NOx control

New MR fault code through OBD NOx control

The EC directive 2005/55/EC has come into force since 1st October 2007. For this reason all new IV/V-vehicles are equipped with a NOx sensor which checks the nitrogen oxide concentration in the exhaust gas.

Through the NOx sensor new faults can occur which are stored in the engine control (MR) control unit by the following fault codes:

 1 29 71 Too high nitrogen oxide emission (threshold 1 exceeded)

 1 29 72 Too high nitrogen oxide emission (threshold 2 exceeded)

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The possible causes for these fault codes are diverse and after the repair must be assigned to the corresponding damage code (SSL).

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Assignment of fault code to damage code

1 AdBlue quality
Checking by means of BlueTec test case.
SSL 4700D C8 (AdBlue - wrong version)

2 Metering device
Checking by means of BlueTec test case.
SSL 14473 B2 (metering device clogged)

3 SCR air temperature and air humidity combination sensor
Checking by Star Diagnosis.
Replace if test steps 1 and 2 of the guided troubleshooting in Star Diagnosis are OK.
Damage code 83068 52 (sensor does not operate correctly)

4 Exhaust pipe cracked
Visual inspection.
Replace exhaust pipe
Damage code 49012 07 (exhaust pipe cracked)

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5 SCR catalytic converter deformed/damaged due to accident
Visual inspection.
Replace SCR catalytic converter not a warranty case
If no external deformation/damage of the SCR catalytic converter can be detected, this may only be replaced after consultation with the plant service department.
Damage code 49025 (replace SCR catalytic converter).

 For notes on Bluetec test case, see service information: SI00.00-W-0108A.

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Special case: vehicles operating with vegetable oil

Vehicles which are operated with vegetable oil represent a special case. Chemically unchanged vegetable oil (e.g. rape seed oil, soya bean oil, sun flower oil etc. ) may not be used in Mercedes-Benz diesel engines.

 For this see in WIS BB00.40-P-0135-00A

If the threshold is exceeded, the check of the fuel type can be charged by means of damage code 14200 A8 (exhaust aftertreatment - wrong operating fluid).

The elimination of excess nitrogen oxide due to vegetable oil on the other hand cannot be charged to the warranty.

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Notes for troubleshooting

Support for troubleshooting is stored in TIPS. If no troubleshooting is found during diagnosis, damage code 14200 (exhaust aftertreatment) should be used.

Depending on the fault code the corresponding damage type should be coded in the MR control unit:

 1 29 71 Too high nitrogen oxide emission (threshold 1 exceeded)
 FH: NOx threshold 1 exceeded

 1 29 72 Too high nitrogen oxide emission (threshold 2 exceeded)
 FH: NOx threshold 2 exceeded

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If no fault cause was found during troubleshooting, the Nox control questionnaire stored in TIPS must be filled in and faxed together with the Star Diagnosis printout to the respective MPC.

 After analysis of the questionnaire the MPC or the Wörth plant service department contacts the workshop.

The NOx control questionnaire is enclosed in the TIPS documents as an attachment.

 KG 14.40
NOx control - "NOx emission threshold 1 exceeded" (MR fault code 1 29 71)

 NOx control - "NOx emission threshold 2 exceeded" (MR fault code 1 29 72)

W14.40-1428-03