Advanced Automotive Fault Diagnosis

engines. As diesel engine technology becomes
more sophisticated, so does the requirement for
OBD. In addition, emission legislation is driving
more sophisticated requirements for after treat-
ment of exhaust gas. All of these sub-systems are to
be subjected to checking via the OBD system and
present their own specific challenges. For example,
the monitoring of exhaust after treatment systems
(particulate filters and catalysts) in addition to
more complex EGR and air management systems.
11.3.4 Rate based monitoring
Rate based monitoring will be more significant for
future systems which allows in-use performance
ratio information to be logged. It is a standardised
method of measuring monitoring frequency and
filters out the affect of short trips, infrequent jour-
neys etc. as factors which could affect the OBD
logging and reactions. It is an essential part of the
evaluation where driving habits or patterns are not
known and it ensures that monitors run efficiently
in use and detect faults in a timely and appropriate
manner. It is defined as:
Minimum frequency ⫽ N/D
Where N ⫽ number of times a monitor has run,
D ⫽ number of times vehicle has been operated.
11.3.5 Model based development
A significant factor in the development of any
future system will be the implementation of the
latest technologies with respect to hardware and
software development. Model based development
and calibration of the system will dramatically
reduce the testing time by reducing the number of
test iterations required. This technique is quite
common for developing engine specific calibra-
tions for ECUs during the engine development
phase (Figure 11.4).
Hardware-in-loop (HIL) simulation plays a part
in rapid development of any hardware. New hard-
ware can be tested and validated under a number
of simulated conditions and its performance veri-
fied before it even goes near any prototype vehicle.
The following tasks can be performed with this
technology.
●
Full automation of testing for OBD 
functionality.
●
Testing parameter extremes.
●
Testing of experimental designs.
●
Regression testing of new designs of software
and hardware.
●
Automatic documentation of results.
11.3.6 Comment
What with the possibility of navigation systems
reporting where we are, speed and traffic light
cameras everywhere and monitoring systems
informing the authorities about the condition of
our vehicles, whatever will be next?!

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