obd gps vehicle diagnostic system

The full name of obd gps: On Board Diagnostics is translated into Chinese: It is a detection system extended for car fault diagnosis. "Obd ii gps" is "on Board Diagnostics Ⅱ", the abbreviation for Type Ⅱ on-board diagnostic system. In order to standardize the diagnosis of vehicle emissions and driveability-related faults, starting from 1996, all new vehicles sold in the United States must have similar diagnostic equipment, fault codes and repair procedures, that is, comply with obd ii gps program regulations. With the increasing degree of economic globalization and automobile internationalization, the obd ii gps system will be more and more widely implemented and applied as the basis for driving and emission diagnosis. The obd ii gps program makes car fault diagnosis simple and uniform, and maintenance personnel do not need to learn new systems from each manufacturer.

How obd gps works

The obd gps system will monitor whether the car's exhaust exceeds the limit from the engine's operating status at any time, and will immediately issue a warning if it exceeds the limit. When the system fails, the fault (MIL) light or check engine (Check Engine) warning light is on, and the powertrain control module (PCM) stores the fault information in the memory, and the fault code can be read from the PCM through a certain program . According to the prompt of the fault code, the maintenance personnel can quickly and accurately determine the nature and location of the fault.

obd gps monitors the engine, catalytic converter, particle trap, oxygen sensor, emission control system, fuel system, EGR and other systems and components in real time. Then connect to the ECU [electronic control unit, which can detect and analyze the function of emission-related failures] through different emission-related component information. When an emission failure occurs, the ECU records the failure information and related codes, and sends it out through the failure light Warning, inform the driver. ECU guarantees the access and processing of fault information through standard data interface.

The development of obd gps

The obd gps technology originated in the United States in the 1980s. The early obd gps technology used appropriate technical methods to alert drivers to failures or malfunctions. The European Union and Japan introduced obd gps technology after 2000. After 2004, the obd gps technology of developed automotive countries will go to the third stage.

There are certain differences in obd gps detection items and limits between Europe and the United States, and the specific differences will not be described in detail. The purpose of obd gps monitoring in the United States is to detect failures before becoming high-emission vehicles; the purpose of obd gps monitoring in Europe is to find high-emission vehicles. The obd gps technology imported by our country will adopt the relevant regulations of the European obd gps system after three phases.

The author and automotive technicians have determined that Euro III emission standards are not equivalent to obd gps. After the mandatory obd gps installation policy implemented by Beijing on December 1, vehicles will comply with Euro III+obd gps standards.

Obd gps needs to declare that vehicles are equipped with obd gps, which requires a systematic application process, and requires companies to conduct multiple tests on vehicles equipped with obd gps and provide relevant departments with data that meet the standards (currently 3 mandatory inspection items are oxygen sensor failure Verification, catalytic converter failure verification, misfire verification), the cycle is generally 10 months. Vehicles equipped with obd gps need to re-apply for vehicle announcements. The research and development cost of obd gps is very high, if the large-scale production is realized, the technical cost shared by a single unit will be reduced.

The role of obd gps

After the obd ii gps plan is implemented, any technician can use the same diagnostic instrument to diagnose any car produced according to the standard. One of the mature functions of obd ii gps is to record the data of all sensors and drivers when the system lights up the fault light, which can meet the needs of diagnosis and maintenance to the greatest extent. In the face of increasingly stringent vehicle emission regulations in various countries, the goal of obd ii gps monitoring the efficiency of the emission control system is: as the efficiency of the vehicle operation decreases, according to the federal test procedure, when the vehicle emission level has reached 1.5 times the new vehicle emission standard, Turn on the fault light and store the fault code. In addition, obd gps Ⅱ also requires some additional sensor hardware, such as an additional heated oxygen sensor, installed downstream of the catalytic converter exhaust. A more precise crankshaft or camshaft position sensor is used to more accurately detect whether there is a misfire. All models are equipped with a new 16-pin diagnostic interface. In this way, the computer's ability is greatly improved, not only can track the damage of components, but also meet the strict restrictions on vehicle emissions.

Repair the obd gps system in time if it fails. The once-a-year vehicle inspection has limited effect on controlling vehicle emissions. But after the obd gps is installed in the car, it is completely different. It can monitor the car's emission level at any time.

If the emission is not up to standard, obd gps will issue a warning and promptly notify the driver to repair it. The most important thing for Euro III is to use obd gps.

When performing fault diagnosis on cars such as Shanghai Buick and Guangzhou Accord, the self-diagnostic system can display standard obd ii gps fault codes, such as "PO125" and "PO204", which respectively indicate that the engine does not reach 10°C and within 5 minutes when there is a speed signal. The No. 4 injector output driver incorrectly responds to the control signal.

SAE J2010 specifies a 5-digit standard fault code, the first digit is a letter, and the last 4 digits are numbers.

The first letter indicates the system where the fault code is set. There are currently 4 letters assigned: "P" stands for power system, "B" stands for body, "C" stands for chassis, and "u" stands for undefined system.

The second character is 0, 1, 2 or 3, and the meaning is as follows: 0-General fault code defined by SAE (Society of Automotive Engineers): 1-Extended fault code defined by automobile manufacturers; 2 or 3-with system Different characters (P, B, C or U). Power system fault code (P) 2 or 3 is reserved by SAE for future use; body or chassis fault code 2 is reserved by the manufacturer, and body or chassis fault code 3 is reserved by SAE.

The third character indicates the malfunctioning system: 1——Fuel or air metering failure; 2——Fuel or air metering failure; 3——Ignition failure or engine misfire; 4——Auxiliary emission control system failure; 5—— Car or idle speed control system failure; 6-computer or output circuit failure. 7——Transmission control system; 8——Transmission control system.

The last two characters indicate the condition that triggers the fault code. Different sensors, actuators, and circuits are assigned numbers in different sections. The smaller number in the section indicates a general fault, that is, a general fault code; the larger number indicates an extended code, which provides more specific information, such as low voltage. Or high, slow response, or signal out of range.

obd gps system structure

scanner

The obd ii gps regulations stipulate fault codes, a large number of engine management sensor signals, computer commands, etc., which can be read out by a general scanning tool. Scanning tools can give a lot of important maintenance information, but many maintenance personnel do not use all of its functions and are only used to read fault codes. In fact, most of the data provided by the scanning tool can be used to locate the fault. A particularly effective troubleshooting method is to use the scanning tool and the four-gas (HC, CO, oxygen and carbon dioxide) or five-gas (plus NOx) infrared exhaust gas analyzer at the same time. In this way, the sensor signal or computer command information can be compared with the actual tailpipe exhaust to see if the logical result of these readings is reasonable.

The test mode is common to all obd ii gps cars and can be tested using obd ii gps scanning tools.

The scanning tool that meets the obd ii gps requirements must be able to access and interpret the emission-related diagnostic trouble codes of any vehicle model. The scanning tool's cable harness can be connected to a standard 16-pin connector.

Oscilloscope

As long as the scanning tool is normal, it tells the user how the engine is working, but the reader still can’t "see" the problem or the scanning tool can’t display it because the "false signal" happens too fast, or the obd ii gps system is not programmed to recognize this at all. Kind of difference. In response to this situation, using a laboratory oscilloscope is very effective. There are desktop oscilloscopes and handheld oscilloscopes. It has been decades for the use of an analog oscilloscope to check the malfunction of the ignition system, but it is completely different from the modern laboratory oscilloscope. The traditional analog oscilloscope requires the displayed signal to be a repetitive periodic signal, while the laboratory oscilloscope displays this signal in real time. Because the sampling frequency is high, every important detail of the signal is displayed, so that the high speed can identify any signal that can cause malfunction when the engine is running. If necessary, you can review the waveforms at any time, because these waveforms can be stored in the memory.

A typical modern laboratory oscilloscope has two-wire or multi-wire capabilities. That is, two or more separate signals can be seen on the screen at the same time. In this way, it is possible to observe how one signal affects another signal. For example, the oxygen sensor voltage signal can be input to channel A, and the injector pulse can be input to channel B, and then observe whether the pulse responds to the change of the oxygen sensor signal.

The laboratory oscilloscope can be regarded as a high-speed visual voltmeter. A clear signal waveform can be seen, and instantaneous interference, spikes, noise, and abnormal waveforms of the measured components can be captured on the graph.

One point worth noting: obd gps only alarms when the emission is not up to standard, but if the oil is not up to standard, installing obd gps will be useless. It is understood that some domestic joint venture automobile factories introduced some models from China and will also be sold in Europe at the same time. They are equipped with obd gps at the beginning of production and have reached Euro III or even Euro IV standards. After domestic production, they will subtract or close obd gps. One major reason is to avoid alarms caused by unqualified oil products, which may cause unnecessary trouble.

interface

The obd ii gps program is designed to avoid confusion between systems. This requires not only the use of a standard 16-pin diagnostic interface, but also the use of specific codes and descriptions of the components in the manufacturer’s documents. This is to achieve the following Unification and standardization.

For example, the device that provides information on the crankshaft position and speed for the computer is called the crankshaft position sensor, which is abbreviated as "CKP", and the computer is collectively referred to as "PCM".

Each car is equipped with a 16-pin diagnostic interface of standard shape and size. Each pin has the same signal distribution and is located in the same position. It is installed under the dashboard, somewhere between the left of the dashboard and 300mm from the right of the center line of the car. Place. It should be noted that certain terminals of the diagnostic interface are designated as specific signals as shown in the attached table. The other terminals can be used by the manufacturer, or have not been used in the current model of the car.

letter of agreement

Manufacturers are required to use the same multi-channel communication language to communicate between PCM and its sensors and actuators, as well as to send and receive diagnostic information between diagnostic tools. The obd ii gps standard requires the engine management system to detect each monitored circuit in the monitoring sequence according to specially set operating conditions such as warm-up period, drive period, obd ii gps stroke, obd ii gps drive period, and similar conditions. Faults, location fault codes, lighting and extinguishing fault lights, and erasing fault codes. Here, the so-called monitoring sequence is a running process, an operation used to test the functions or components of the specified system. For example, the computer can open or close the EGR valve when decelerating, and monitor the MAP sensor to observe whether the EGR valve is working; or when cruising, the computer can open or close the carbon canister purge to observe the signal of the oxygen sensor, so that it can test two parts at the same time.

The problems faced by the introduction of obd gps

The introduction of obd gps is closely related to the four main aspects of use environment, fuel characteristics, driving habits, and vehicle conditions. Shortcomings in any of these links will affect the expansion and application of obd gps. The introduction of obd gps technology requires the corresponding improvement of the following related supporting conditions: fuel quality, vehicle maintenance skills, consistency of related parts and components, the improvement of the driver's level, the improvement of obd gps technology itself and the support of all aspects of society. The author believes that in a certain period of time, my country's obd gps technology is a process of introduction, adaptation, and digestion. Because obd gps technology is not only related to the car itself, but also to other links such as fuel and drivers, the introduction and expansion of obd gps technology is a test and improvement to the automotive industry chain.