汽车电脑板维修基础知识（Basic knowledge of automobile computer board maintenance）

汽车电脑板维修基础知识（Basic knowledge of automobile computer board maintenance） 汽车电脑板维修基础知识(Basic knowledge of automobile computer board maintenance) Voltage signal 1. analog voltage signal The analog voltage signal varies continuously over a certain range. When using a rheostat to control 1 5V bulbs, the rheostat voltage may be any value between 0V-5V. If the varistor voltage is low, then the current flowing through the bulb is small, the bulb is light, and if the rheostat voltage is 5V, the current increases, and the brightness of the bulb increases. The brightness of the bulb decreases as the rheostat voltage drops. This is an example of analog voltage (Figure L). Most sensors in the automotive computer system produce analog voltages. Note: the analog voltage signal varies continuously within the specified range. 2. digital voltage signal If the ordinary pass / break switch is connected to the 5V light bulb, and when the switch is off, the voltage on the bulb is 0V. When the switch is on, the 5V voltage signal is added to the bulb, which lights up and reaches maximum brightness. If the switch is switched off, the voltage on the light bulb goes back to 0V, and the bulb goes out. It is obvious that the voltage signal added to the bulb is either 0V or 5V, or we can say that the voltage signal is not high or low. The voltage signal is called a digital signal. If the switch is switched on and off quickly, then the digital rectangular wave voltage signal is sent to the bulb via a switch (Figure 2). In a car computer, microprocessors include many micro switches. These switches produce a lot of digital voltage signals per second. These digital voltage signals are used to control the length of the component numbers in each relay and system for precise control (Fig. 3). Note: the digital voltage signal is either high or low; the digital signal is called a square wave signal. 3. binary code We have said that the digital signals are either high or low. Therefore, the digital signals can be assigned. For example, a low level digital signal may be specified as 0, while a high level digital signal is set to 1. The assignment of a digital signal is called binary encoding. "Binary" stands for two numbers, and in binary coded systems, the two numbers are 0 and 1 (Figure 4); in car computers, messages are transmitted in binary code. Status, quantity, and text can be expressed in a series of 0 and 1. Many input sensors work within the 0V-5V range. The voltage generated by the throttle position sensor (TPS) is: Turn off the throttle - 0V-2V Partially opened throttle - 2V-4V Large opening valve - 4V-5V The computer can specify a value of 1 for each voltage: 0V-2V - 1 2V-4V - 2 4V-5V - 3 Note: binary code is the numerical value of the signal fit. Two, input adjustment 1. zoom in Some input sensors, such as oxygen (O2) sensors, produce only very low voltage signals less than lV. A very small current is produced accordingly. Therefore, such signals must be amplified or amplified before being transmitted to the microprocessor. Amplification is accomplished by an amplifier circuit in the input adjustment of the computer (Figure 5). Note: the input signal amplification means that these signals are amplified and increased before they are useful to the computer. 2. modulus / number (A/D) conversion Because the input sensor generates analog signals and the microprocessor operates on digital signals, analog signals must be converted to digital signals. The work is done by computer input, adjusting the converter in the chip (Figure 6). The A/D converter continuously extracts the analog input signal at constant time intervals. If the A/D converter of solar term door position sensor signal sampling, the sampling voltage is 5V, the A/D converter sampling voltage firstly quantified, then A/D converter and then the quantization results into binary code 11 (Figure 7). Therefore, we can understand that the A/D converter samples the input sensor signal continuously and quantifies the sampling voltage. The A/D converter then converts the quantization results into binary code. In some car computer, with input chip microprocessor together with adjustment. Three, micro processor 1. structure The microprocessor is calculated and the determination of chip computer. In the micro processor has thousands of transistors and diodes, the triode electronic switch to or on or off the role. The micro processor element in etching in integrated circuit as a hand finger size (IC) plate (Figure 8), a silicon integrated circuit mounted in a rectangular box to protect the flat, metal pins sticking out from both sides of the microprocessor box. These pins are connected with the microprocessor circuit board in a computer. The microprocessor is supported by the memory chips, which store information and auxiliary microprocessor to judge. Looks like a memory chip microprocessor chip, we will explain the memory circuit board function later. Note: the microprocessor chip is calculated and determined in the computer chip. 2. program The program is a set of acceptable to the microprocessor instruction program, the microprocessor introduced state determination. For example, the program can search information sent by the microprocessor sensor, microprocessor and tell how to handle this information. Finally, the program will instruct the microprocessor relay or solenoid trigger output type control device. All kinds of memory stored procedures and other vehicle data. The microprocessor with these data are calculated, when the micro processor operation and decision, microprocessor and memory in the following manner: 1. microprocessor read from the memory information. 2. microprocessor new information is written into the memory. 3. information storage There are many different memory storage unit. Storage unit and file folder box in similar, and each unit has 1 pieces of information. The distribution of 1 addresses of each storage unit. This arrangement of address and folder text or numbers similar. Each address is written in binary code, compiled by the zero sequence start. When the engine works, the computer receives a large amount of information from each sensor. The computer can not deal with all of this information immediately. In addition, some of the time, the computer receives the need to do some judgment information of the sensor. In this case, the microprocessor memory address specified by the information into the memory, and the information is sent to the address (Figure 9). 4. information retrieval When you need to store information, microprocessor specified memory address, and request information processing. When the stored information need to be processed when the specified address, memory copy sent this information to the microprocessor (Figure 10). The original in the storage of information is still in the memory address. The working conditions of storage under various idling air-fuel ratio. The sensor will be operating notice of engine and vehicle computer. The microprocessor is read from a memory idle air-fuel ratio, and the sensor input is compared. In comparison, the microprocessor to make the necessary decisions, and control the fuel injector to provide the required engine air-fuel ratio. Repair of high-grade car moststressful, is the car of the computer. Repair personnel have computer failure, not one that is computer problems, and because of the high price of the computer and not easily decided to purchase a replacement; two is not easy to find similar computer products to substitution test; three is even found similar computer products (such as a car of the same type). Don't trade Changran computer board good plug up test, because the computer is often damaged by external circuit failure caused by the. People are wondering: when you make a car electrician asks for a circuit component condition, a considerable number of electrician will be to "power" or "no power" to answer, if the repair electrical level just stay in the "to" 'or "no power" the state, is not enough for the computer and control system of automobile repairing. Because the failure to determine whether a component and its related lines, At least you must figure out where line is connected with the long-term power supply (+BATT); where the line is connected to the ignition control of a power switch (+B); which is connected to the power supply from the computer provides (+5V); which is the grounding wire; which belongs to the signal line, the signal line with digital 000 with the "logic" of file level test, or "frequency" gear signal frequency measurement under the operating condition (Hz), of course, it is best to use the oscilloscope observation signal waveform. The following combination of automobile computer board repair experience, the principle of car computers and maintenance methods to do a brief summary and presentation, in the hope that the majority of repair technicians benefit. First of all, we need to have a general idea of the internal structure of the car computer. The automobile computer consists of the following parts: 1. automotive computer components 1.1 power supply section The utility model is used for filtering and stabilizing the power supply provided by the automobile to provide a stable DC power supply inside the computer. 1.2 central processing unit (CPU) Cars usually use 8 or 16 bit processors, that is to say, it can control, calculate and transmit 8 or 16 bit binary digits at a time, which is the central command of the computer. 1.3 memory section Used to store programs and all kinds of data, and can be divided into: 1.3.l read only memory (ROM) A computer program used to store a computer; that is, some programs necessary for the computer to run itself. 1.3.2 programmable read only memory (EPROM or EEPROM) A control program used to store the execution of an actuator or other control device. Such as: fuel injection control, ignition advance angle control. Program for idle control and self diagnostics. 1.3.3 random access memory (RAM) Used to temporarily store data from various sensors for use by the central processing unit and also store the system's fault codes. The contents of the random memory will disappear after power cut. 1.3.4 adaptive memory (a type of random storage) used for self learning of computer and automatically adjusting relevant parameters according to condition changes. Such as "idle learning" and so on. 1.4 input / output section 1.4.1 input section The analog signal will be transmitted from the sensors are converted into digital signals (ND conversion) for the central processor, there are some direct digital signal coming from the sensor, without conversion, but the need for plastic, for example: crankshaft position sensor from the signal. 1.4.2 output section The central processor to the signal transmitted by each sensor after receiving after processing, and then a corresponding control signal; the control signal is first converted to digital signals into analog signal (D/A conversion) and then by the power amplifier can be amplified to drive the implementation of device. Some of the output signals do not need to be converted and output directly to the actuating element after amplification. For example, the control of the injector is added directly to the injector coil by amplifying the digital signal. Before starting a computer, the control circuit of the computer (i.e. the external circuit) is checked and the faults in the circuit are eliminated. Because if there is a fault in the outer circuit, the computer can be mistakenly repaired, and even if a new computer board is repaired or bought back, the computer can be damaged again because of the fault of the external circuit. For example: a repair shop will be a crown 28 sedan from the right direction to the left direction, the start can not start, and after several electrical inspection repeatedly failed to find out the problem, it is suspected of computer damage, but can not decide. After checking the external circuit (because changed the direction of the car need to change the line, may take the wrong line), found two color and line size are the same line of engine computer harness, a position sensor to the solar term door, another path to ignition amplifier, it is possible for color and the thickness of the same and the wrong suspect that the two line. Open the computer box, Abbreviation view is connected with the two lines of computer pins on the circuit board, found a "IDL", another is "IGL", and "IDL" to the ignition amplifier, and the "IGT" to the solar term door position sensor. So far, it can be decided that the two lines are connected and should be exchanged with each other. Because "IGT" is "IGNIROT" (i.e. English igniter) abbreviation, and "IDL" is English "IDLE" (i.e., idle, idle valve position sensor on the knuckles for contact). The two lines were switched on and the test engines run. This example: repair or replace the computer must check the external circuit, otherwise prone to be bad or good computer repair computer installed a new fault also cannot be eliminated, even the new computer and burn etc..