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On-Board Diagnosis, Function - GF07.10-P-1020OGF

ENGINE 642.8 in MODEL 166 

as of model year 2016 

ENGINE 642.8 in MODEL 292 

Function requirements for European On-Board Diagnosis (EOBD), general points 

European OBD (OBD), general 

An On-Board Diagnosis system of the second generation is used (EOBD II)). In Europe the EOBD II, with the respective adaptations for the European market, is called the European On-Board Diagnosis (EOBD). The OBD system is integrated in the CDI control unit (N3/9) and has the following tasks:

EOBD pursues the follow objectives:

The following components and systems are monitored:

Function sequence for the European On-Board Diagnosis (EOBD) 

The EOBD is described in the following steps:

Function sequence for fault detection 

The CDI control unit checks itself and its input and output signals for plausibility and detects possible malfunctions.

The faults and their storage are differentiated between as follows:

The following faults are recognized according to their frequency and duration:

Function sequence for test procedure 

One differentiates for test procedures between component checking and function chain test.

Component checking 

The component checking is direct checking of a component. It includes:

The following three test results can occur:

Function chain test 

The function chain test is indirect checking of the effect of controlled change. Here individual components and systems are checked which cannot be checked over a component checking. The function chain is a controlled procedure of cause and effect. The CDI control unit controls one or more components (cause) and evaluates the resulting sensor signals (effect). In the process the CDI control unit compares the sensor signals with stored comparative values and thus recognizes trouble-free or not trouble-free functioning of components and systems.

The following are monitored over function chain tests:

Function sequence for cyclic monitoring 

Cyclic monitoring takes place for components and systems which are not permanently active. Regeneration, for example, only takes place when the vehicle is being operated under partial-load conditions and can therefore only be monitored during this operating phase.

The following components and systems are monitored cyclically:

Function sequence for continuous monitoring 

Continuous monitoring means continuous monitoring from engine start to "ignition OFF".

The following components and systems are monitored continuously:

Function sequence for Readiness Code 

In order to obtain a statement about freedom from faults of cyclically monitored components and systems during read out of the fault memory, there must be test readiness for this. The test readiness of a component or a system is shown using the readiness code. The readiness code tells you whether fault detection tests have been run at least once, indicating that the components or the system is active.

The readiness is determined at least once per driving cycle and the readiness code is set for a given readiness. To set the readiness code it is sufficient if the vehicle has checked all components associated with the system at least once.

The test result for setting the readiness code is not important. This means that it will also be set if a fault is found in the systems or the component.

The readiness code is set for the following components and systems once they have been tested:

If the test readiness of individual systems or components is not given then these can be created using the diagnostic unit. To do this the function chain sequence is started manually over a menu item of the software.

IMPORTANT

All readiness codes are reset automatically when deleting DTCs.

Function sequence for error saving 

Emissions-relevant malfunctions just found from the current and previous driving cycle are temporarily stored in the EOBD until confirmed (through occurrence in two consecutive driving cycles) in the form of a fault code, also called a diagnostic trouble code or DTC.

If a found malfunction occurs in two consecutive driving cycles, the fault code is stored in the CDI control unit fault memory after the second driving cycle is completed.

IMPORTANT Driving cycle

A driving cycle consists of an engine start, vehicle journey and stopping the engine, whereby an increase in coolant temperature by at least 22°C up to at least 70°C must occur during travel.

Function sequence for avoiding consequential faults 

If a faulty signal is recognized and stored all tests are broken off for which this signal is need as a comparative value (so-called transverse locking). Saving of consequential faults is thereby prevented.

Function sequence for saving the fault freeze frame data 

Besides the malfunctions, the operating conditions under which they occurred are also stored as so-called fault freeze frame data.

If the fault occurs a second time then also these fault freeze frame data are stored. If the fault continues to occur then the last stored fault freeze frame data is updated. The fault freeze frame data can be read out for the first and last occurrence of a fault.

Fault freeze frame data are, for example:

Function sequence for fault message 

The engine diagnosis indicator lamp in the instrument cluster (A1) is actuated by the CDI control unit via chassis CAN 1 (CAN E1), the electronic ignition lock control unit (N73) and chassis CAN 2 (CAN E2). If a fault occurs in two driving cycles, one after the other, the indicator lamp engine diagnosis lights up. In the case of catalytic converter damage caused by ignition misfires the engine diagnosis indicator lamp flashes for as long as the ignition misfires occur and then lights up permanently during the whole (remaining) driving cycle.

Fault message by means of the engine diagnosis indicator lamp goes out automatically after 3 consecutive trouble-free driving cycles.

Function sequence for reading out the fault memory 

The CDI control unit is connected via chassis CAN 1, the electronic ignition lock control unit and the diagnostic CAN (CAN D) with the diagnostic connector. Stored DTCs and their fault freeze frame data as well as the readiness codes can be read out using a commercially available diagnostic equipment or XD for "ignition ON" or for a running engine over the diagnostic connector.

Function sequence for fault clearing 

Stored faults are first deleted automatically after 40 successive trouble-free driving cycle from the fault memory. They can, however, also be deleted (after repair work has been done) using commercially available diagnostic equipment or the Xentry Diagnostics system.

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