Service Information: Changes in testing and repair work by introducing the NOx sensor/OBD NOx control

Legal changes

European legislation specifies a permanent monitoring of the nitrogen oxide (NOx) content in the exhaust gas for all new vehicle registrations as of 01.October 2007. For this reason as of 06/2007 BLUETEC vehicles are being gradually equipped with NOx-sensors.

The vehicles have:

 Code KE8 on-board-diagnosis (OBD) 1, with NOx control

or

 Code KE9 on-board-diagnosis (OBD) 2, with NOx control

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Exceeding the NOx-value slightly is displayed by a flashing indicator lamp (Malfunction Indicator Lamp [MIL]) in the dashboard. Exceeding the NOx value by an amount which is above a set limit value furthermore leads to engine torque limitation.

This involves a legal requirement which must be kept to by each vehicle manufacturer.

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Changes in testing and repair work

The following changes in testing and repair work result from the introduction of the NOx sensor:

1. New test equipment/methods

2. Resetting of current OBD NOx control-relevant engine control (MR) fault code or torque limitation only via vehicle documentation system

3. Adjustment of the correct torque limitation after replacing the drive control (FR) control unit

1. New test equipment/methods

If the vehicle electronics detects that the NOx value is exceeded, a fault code is stored in the engine control (MR) control unit. In order to carry out guided troubleshooting, test equipment is required in order to be able to determine the urea concentration in the AdBlue fluid or the metering quantity of the metering device for example.

A corresponding test kit can be seen in GOTIS
http://gotis.aftersales.mercedes-benz.com

under: workshop equipment - Chapter D - Group 09/14/49 - subject 01.0.

In addition some series production parts which are used as test tools can be obtained via the Global Logistics Center Germersheim.

The use of test equipment is described in the test and repair instructions and will be published in the next few months.

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The test kit M102000 contains the following test tools:

 Refractometer for determining the urea content

 Liquid siphon

 Silicone hose; outside diameter - 9 mm; inside diameter 6 mm; length 3.50 m

 Bottle 1000 ml with screw cap

 Measuring cylinder 500 ml

 The test kit should be ordered without delay.

Parts which are to be obtained via Global Logistics Center Germersheim:

 A 541 140 08 55 Test injection line
for vehicles with engine model series 500 and 900

 A 457 140 11 55 Test injection line
for vehicles with engine model series 457

 A 000 140 03 68Test injection nozzle

 The injection nozzle and injection lines can wear at the cutting ring screwed connection and must therefore be replaced by new parts from time to time.

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2. Resetting of current OBD NOx control-relevant engine control (MR)fault code or torque limitation

Resetting of current OBD NOx control-relevant engine control (MR) fault code or torque limitation is only possible via the vehicle documentation system

After carrying out a repair on a vehicle on which exceeding of the nitrogen oxide level is currently stored in the MR control unit, the fault code cannot be reset immediately by STAR DIAGNOSIS.

An encrypted random number must be determined via the vehicle documentation system (screen 1801) analog to the process "Teach in key". After entry of the encrypted random number in the STAR DIAGNOSIS the fault code and any torque limitation associated with it is reset. This involves a legal requirement which must be kept to by each vehicle manufacturer.

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Without vehicle documentation system access a test drive lasting possibly several hours must be performed after a repair has been carried out to reset the current fault code In the process the MIL lamp must change from flashing to steady light or go out.

After the current fault code was reset to "stored", this can be erased with the help of STAR DIAGNOSIS.

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3. Adjustment of the correct torque limitation after replacing the drive control (FR) control unit

The following torque limitations are adjusted on commercial vehicles ex plant as per the legal requirements:

Vehicles with permissible gross vehicle weight >16 t:

 60 % of max. torque

Vehicles with permissible gross vehicle weight <16 t:

 75 % of max. torque

Vehicles with special rights due to official tasks (army, federal police, fire brigade, rescue service, disaster control, customs, etc.)

 No torque limitation

 Official vehicles are marked with the code ZD1 (vehicles with official tasks).

FR control units from GLC Germersheim are always supplied with a torque limitation which is parameterized to 60 % of the maximum torque. Therefore on vehicles with permissible gross vehicle weight  16 t or vehicles with official tasks the parameter must be adapted manually after a control unit replacement.

So that the parameter can be adapted in the FR control unit via STAR DIAGNOSIS, an encrypted random number must be determined via the vehicle documentation system exactly as under section 2.