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Video Electr. Eng. Managem.
Video Outside Mixt. Prepar.
Video Intern. Mixt. Form.
Video Dir. Petrol Injection
Video Exh. Gas Treatment
Video Exhaust Gas Recirc.
Video Emission Test (petrol)
Video Emission Test (diesel)
Video Adj. Intake Manifold
Video Adjustable Camshaft
Video Var. Mech. Valve Lift
Video Electr. Accel. Pedal
Video Fuel Shut-off
Video Pressure Sensor
Video Knock Sensor
Video Throttle Potentiom.
Video LE-motronic
Video OBD-data logger
Video On Board Diagnosis 1
Video On Board Diagnosis 2
Video On Board Diagnosis 3
Video On Board Diagnosis 4

          A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

  On Board Diagnosis

Research: Andrea Hieble / Andreas Sachse


The figure on top shows a Motronic with E gas, sequential injection, pre-catalyst and post-catalyst probe. In this example a 16-pole plug enables, in principle, anyone to carry out a check of the engine management system with a suitable scan tool. The data profundity depends on the work clearance.

How it works

OBD became possible among other things due to a post-catalyst lambda sensor (two-step finger sensor). Not only the final exhaust gas can be checked, but also the proper working of single cylinders by paced comparison with the pre-catalyst probe. (broad-band lambda oxygen sensor) Because of various regulations it was introduced first in vehicles produced for the American market (California). In Europe all newly registered petrol engine vehicles from the year 2000 onwards must have OBD, likewise all diesel vehicles starting in the year 2004.

Another, very important advantage is the possibility of changing the software. Qualities of the engine - even its performance - can be changed if you transmit new identity fields and new programmes via the OBD interface to the control device. "Chip tuning" is outdated because there is no chip to replace any more. Besides, the data can be transferred even on the road by (mobile) phone. It is just a matter of time, until this system will be transferred to all electronically controlled components on board.
The exhaustive implementation of this system will also have its effect on the design of vehicles. Electronic systems will be formed in such a way that future additional changes are as much as possible software changes with little hardware impact. When the car is checked on a routine basis, a regular update is possible. Hopefully, once implemented the initial solutions are not much less matured because corrections afterwards have become much easier.               Top of page               Index
2001-2015 Copyright programs, texts, animations, pictures: H. Huppertz - E-Mail
Translator: Don Leslie - Email:

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