Faster and more efficient: new processes for on-board diagnostics!

The on-board diagnosis detects whether the emission-relevant systems in the vehicle are working properly. Conformity with the legal requirements is checked before production starts and verified later in the ongoing series. Porsche Engineering increases efficiency with test and simulation tools developed in-house.

The on-board diagnosis (OBD) monitors the functionality of components relevant to emissions over the life of the vehicle. To do this, it carries out test routines that are implemented in all relevant control units of the vehicle and that run while the vehicle is in motion. If a control unit gives implausible feedback, a corresponding code is stored in the control unit's OBD fault memory - for example, if a lambda probe no longer correctly recognizes the oxygen content in the exhaust gas and the engine management system then changes the combustion parameters. At the same time, the yellow engine control light in the cockpit lights up.

OBD originated in the United States: it was introduced in California in 1988 and across the United States in 1994. Two years later, stricter exhaust gas limits resulted in the more powerful OBD-II system, which is still in use today, which monitors emissions more precisely, includes other components in the check and offers more detailed diagnostic options for workshops. In Europe, OBD became compulsory in 2001, albeit with partly different requirements than in the USA. Above all, the emission limit values ​​and measurement cycles differ significantly from one another. Other regions such as China followed in the years that followed.

OBD was first introduced in California in 1988 and across the United States in 1994. It has also been mandatory in Europe since 2001. China and other regions followed in the years that followed.

The OBD test of a new vehicle model at Porsche is basically divided into three steps: firstly, quality assurance tests while the vehicle is being coordinated, secondly, typing tests in the so-called OBD demo phase as a mandatory approval requirement, and thirdly, after the start of series production, a comprehensive examination of all potential OBD- Error memory entries on vehicles from ongoing production. Throughout all phases, Porsche Engineering and Porsche AG maintain a partnership that has grown over many years. “As a rule, we start checking the OBD application about six months before the start of series production. If the examinations reveal any abnormalities, we analyze the causes and suggest possible remedial measures, ”says Dr. Matthias Bach, head of the engine application and mechanics discipline at Porsche Engineering, whose field includes on-board diagnostics.

Coordination with certification authorities

In the subsequent OBD demo phase, it is demonstrated that the vehicle's OBD system complies with the legal requirements. To this end, Porsche AG coordinates test series with the certification authorities in the individual regions around the world, which the experts from the Porsche Engineering testing department work through. "We cover 145 markets, ten of them with individual approval modalities," says Thomas Rauner, head of the drive typing department at Porsche AG. The different emissions legislation, test cycles and OBD requirements make development and testing extremely complex. A recent example is China, where the China 2023b directive, which will apply from 6, specifies demanding OBD test conditions. “In contrast to the rest of the world, in China a positive test report is no longer sufficient to certify a new vehicle model. Rather, the OBD test must be carried out on site and under the supervision of the authorities, ”explains Dr. Sebastian Rüger, who is responsible for OBD certification at Porsche AG.

There are 3.500 possible error codes in the areas of chassis and drive in hybrid vehicles.

As a strategic exclusive partner of Porsche China, Porsche Engineering supports the on-site certification through technical services such as the implementation of the test series. Porsche AG coordinates the test results with the respective certification authorities. "Thanks to the trusting cooperation and the continuous exchange of information between the colleagues from Porsche Engineering in China and Germany as well as Porsche AG, we can implement the approval of the vehicle model within a tight timeframe," says Rauner.

For the typing tests of a new vehicle model, Porsche Engineering carries out up to 80 test runs on the roller dynamometer and simulates various emission-related events such as a damaged lambda probe line. For example, the engineers build specially prepared components into the vehicle or simulate predefined fault cases. In order to simulate the wear and tear over many years, they also use components such as catalytic converters that have undergone an artificial aging process.

In addition to the legal requirements, the constantly increasing number of electronic systems in the vehicle is also leading to greater OBD complexity. The OBD not only monitors individual components, but also checks entire functional processes, including potential cross-influences from other vehicle systems.

"We cover 145 markets, ten of them with individual approval modalities." Thomas Rauner, Head of the Drive Typing Department at Porsche AG

This also includes control units that could indirectly influence emissions in the event of a defect, for example for the adaptive cruise control (ACC), the vehicle dynamics control “Porsche Stability Management” (PSM) and the “Remote Park Assistant” from das The vehicle parks automatically. "As part of the OBD verification tests required by the authorities, the so-called Product Vehicle Evaluation, we have to prove that the emission-neutral substitute measure is being carried out correctly - that is, it no longer has any influence on the vehicle's emissions behavior," says Rüger. "Experts speak of an emissions neutral default action, or ENDA for short." The resulting test effort is correspondingly high: "In modern hybrid vehicles, we have up to 14 control units from the drive and chassis areas with around 3.500 possible error codes," says Bach.

Simulation of defects

These must be verified within a period of up to six months after the start of production of a vehicle. In order to save time and money, Porsche Engineering relies almost exclusively on the simulation of errors. “Instead of installing and removing defective components for test bench investigations or road tests at great expense, we change the respective sensor signals or messages in the vehicle's electronic data system,” explains Bach. This requires a profound understanding of the components and their function in the overall system, which Porsche Engineering, as an OBD service provider, has gained in countless development projects from the very beginning. “Our strength is our know-how in the areas of complete vehicles and testing. On this basis, we have developed our own testing and simulation tools with which around 95 percent of the defects in the OBD system can be reproduced, ”explains Bach.

For example, the function of the throttle valve actuator is simulated externally during engine operation so that the throttle valve installed in the vehicle can be tested separately. In order to display the desired error memory entries for the injectors, specially developed software is used, with which the injection quantity of the injectors can be changed in a very fine range. "When simulating network errors in the electronics architecture, we are always up to date thanks to our good cooperation with our colleagues in development and can therefore already present the appropriate test procedure for introducing new diagnostic functions," says Bach.

"Our strength is our know-how in the areas of complete vehicles and testing." Dr. Matthias Bach, head of the engine application and mechanics discipline at Porsche Engineering

The result is an extremely fast and efficient OBD process. It is foreseeable that the resulting advantages will become even more important in the future, as stricter emission standards, such as the Euro 7 standard that is currently under discussion, will further reduce the permissible exhaust gas limit values ​​worldwide. This means that the spiral for OBD development continues to turn: New systems and functions enable lower emission values, which are then checked again using the improved OBD. In addition, there are diagnostic tasks that result from the use of synthetic fuels, so-called eFuels. “It can be assumed that electric cars will also have to pass an OBD test in the future,” says Bach, venturing a look into the future. "In this case, it would not be about nitrogen oxide or particle emissions, but about the condition of the drive and battery."

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