[maintenance information] fault diagnosis of Audi A4 ESP electronic stability system structure

Category:Fault example - Date:2015-12-10

The structure of Audi A4 electronic stability system ESP and the functions of all components.

the composition of Audi A4 automotive electronic stability system (ESP) can be roughly divided into sensing signal part, control unit and execution control part.

the composition diagram of Audi A4 automotive electronic stability system (ESP).



1 electronic control unit J104

the control unit J104 is mainly responsible for the information operation analysis and control instruction of the whole system. In order to ensure the reliability of the system, there are 2 processors in the system, and the two all use the same software to process the signal data and monitor and compare each other. If the control unit fails, the driver can still do the general brake operation, but the functions of ABS, EDL, EBD, TCS, ESP will all fail, then the &ldquo can be diagnosed; the control unit fault ” or “ the power supply voltage fault ” the fault storage.

2 steering angle sensor G85

the steering angle sensor G85 is the angle measurement based on the grating principle. The G85 is located between the steering lamp switch assembly and the steering wheel, which is integrated in the spiral cable of the airbag. The sensor sends the angle of the steering wheel to the control unit according to the driver's manipulation of the steering wheel to the control unit. The circumference is ± 540° the steering wheel turns 3 cycles. If the sensor has no signal, the vehicle can not determine the driving direction, ESP will fail, then &ldquo can be diagnosed; the sensor has no signal ” “ set error ” “ electronic fault ” “ unreliable signal ” and other fault storage.

3 lateral acceleration sensor G200

lateral acceleration sensor G200 can determine whether the vehicle is subjected to lateral force and the magnitude of lateral force. Without the signal, the control unit will not be able to calculate the actual driving state of the vehicle, the ESP function will be invalid, the &ldquo can be diagnosed; the circuit breaker ” “ the positive pole, the negative electrode short ” the “ the sensor damage ” and so on.

4 yaw rate sensor G202

the yaw rate sensor G202 is mainly used to determine whether the vehicle rotates along the vertical axis and provides rotation rate to the control unit. If there is no measuring value of the yaw rate, the control unit can not measure the turning of the vehicle, the ESP function will fail, and the &ldquo can be diagnosed; the circuit breaker ” the “ the positive pole, the negative electrode short ” the “ the sensor damage ” and so on. In the actual structure, the two are integrated together, together in a cabin box, located in the front dashboard, the center of gravity of the vehicle, so that the size of the installation can be reduced, and the precise matching value can be ensured, and it does not change.

5 speed sensor G44 ~ G47

speed sensor G44 to G47 is used to detect the actual speed of each wheel in order to determine the motion state of the wheel. If there is no signal, the ABS and ESP alarm lights are bright, indicating that the system can not work properly, that is, the function of ABS and ESP fails, and the &ldquo can be diagnosed; the sensor has no signal ” “ the sensor circuit breaker ” and so on.

6 brake sensor G201

the brake sensor G201 notifies the actual pressure of the brake system of the control unit, and the control unit calculates the braking force on the wheel and the size of the longitudinal force of the vehicle. If ESP is adjusting the unstable state, the control unit contains this value within the calculation range of the lateral force, if there is no brake pressure. The force signal system will not be able to calculate the correct lateral force, so ESP fails, so that &ldquo can be diagnosed; circuit breakage ” “ &rdquo of the positive pole short circuit; “ negative short-circuit ” and other faults.

7 ESP button switch E256

press ESP button to switch E256 button, ESP function is turned off, and ESP function is reactivated by pressing the button again. When the ESP adjustment function is going on or over a certain speed, the system will not be shut down, and there are 3 modes of operation: driving out from deep snow or soft ground, skidding the driving wheel to get rid of the trapped state; driving with antiskid chains; driving in the power test state of the vehicle. In these 3 cases, the switch should be in a closed state. When a failure occurs, the ESP can not be closed and the ESP alarm lamp on the combined instrument will alarm. The switch has no self diagnostic function.



8, hydraulic control unit

The brake sub pump is controlled by the solenoid valve of the hydraulic control unit, and through the control of the oil intake valve and the oil outlet valve of the brake sub pump, the 3 working states are established. Here, the author takes the wheel brake process on one of the brake loops as an example to illustrate how the hydraulic unit works. The basic components are: control valve N225 (a), dynamic control high pressure valve N227 (b), oil intake valve (c), oil outlet valve (d), brake cylinder (E), return pump (f), active server (g), low voltage accumulator (H).

during booster, the booster set up the pre pressure to make the reflux pump suck the brake fluid. N225 is closed, N227 is opened, the oil inlet valve remains open, ESP is controlled and adjusted, and the dynamic hydraulic pump (g) begins to transport the brake fluid from the brake fluid storage tank to the brake line. The brake pressure is quickly built in the brake sub pump and the return pump, and the brake fluid is started to transport the brake fluid to further improve the brake pressure.

during the packing process, the inlet valve is closed, and the oil outlet valve is also closed. The brake pressure can not be unloaded. Pump stop working, high pressure valve closed N227 (B).

during the unloading process, the oil outlet valve opens, the N225 pressure is opened or closed, and the N227 and oil inlet valve are closed. The brake fluid is returned to the storage tank through the N225 and the main cylinder.

When the function of the solenoid valve is unreliable, the whole system is closed and the solenoid valve will be diagnosed as “ the circuit breaker ” “ the fault of the positive / negative short circuit ”

9, double stage pump

The double stage oil pump is used to establish brake pressure in the function of ESP. Its structure is shown in Figure 4: in Figure 4 (a), the piston moves to the left, the oil pressure in the cavity 1 rises, the one-way valve opens, the check valve closes, the pressure oil is sent to the brake sub pump, and the vacuum degree in the cavity 2 increases, and the hydraulic oil of the tank will be inhaled. In Figure 4 (b), the piston moves to the right, the pressure rises in the cavity 2, and the cavity 1 pressure drops in the vacuum. Then the check valve opens and the pressure oil in the cavity 2 goes into the cavity 1, and the cavity is filled with 1. When the piston moves again left, the pressure is set up quickly, then the brake pump will quickly brake the wheel, which is the advantage of the oil pump, that is, the pump oil is large, and the pressure is fast.



10, ESP system alarm lamp

ESP system has 3 kinds of warning lights. They are braking system warning lights K118, ABS alarm lights K47, ASR/ESP alarm lights K155. When the system is in a different state, the 3 alarm lights will have different displays, so in the actual application process, it is possible to judge the work of the whole ESP system according to the display of the 3 alarm lights, and the display of the 3 kinds of alarm lights as shown in Figure 5. In addition, when the oil surface in the liquid tank of the brake fluid is too low or when the liquid level sensor is damaged, the alarm lamp K118 will also be lit, but the ESP system will not have a fault storage at this time. Due to other reasons, when the three alarm lights are lit, there will be fault storage in the system.



The self diagnosis function of the two and ESP system

initialization and calibration of.1 and steering wheel angle sensor G85.

if the steering wheel angle sensor G85 is broken down or replaced, the ESP control unit J104 is replaced, or the voltage value of the vehicle is not normal, the calibration value of the sensor will be lost, that is, the control unit can not identify the data starting point and the change rule of the sensor normally, so the initialization calibration is needed again. There are two ways to initialize calibration: road test and VAS5051.

when driving on a short distance, the sensor G85 will be initialized according to the wheel speed sensor information.

the methods and steps of initialization and calibration using diagnostic instrument VAS5051 are:
(1) connect VAG1551 or VAS5051 to 03 address.
(2) choose login 11, confirm by Q key, enter the login password 40168, then press the Q key (when making many adjustments, you only need to log in 1 times).
(3) start the vehicle and run on flat road at a speed of no more than 20km/h.
(4), if the steering wheel is in the middle position (if not in the middle position, need to be adjusted), stop the car, do not adjust the steering wheel, do not close the ignition switch;
(5) select the 08 function of reading data stream, input 004 channels, and observe whether the first display area is -4.5?.5. ? (6), select the basic setting function 04, press Q to confirm, and then enter the group called 001, ABS warning lights flashing;
(7) select the exit function 06. According to the Q key, we confirm that the ABS and ESP alarm lights are about 2S, at the end of the initialization calibration.

2, ESP road test and system test

the role of ESP road test is to check the reliability of each sensor of the ESP system (lateral acceleration sensor -G200, yaw rate sensor -G202 and brake pressure sensor -G201, steering wheel angle sensor -G85). Every time the electrical components of the ESP system are removed or replaced, road tests must be carried out. Note: once the road test for ESP system is started, it cannot be aborted, and it must be completed. The test process is as follows:

(1) (1), connect the diagnostic instrument VAS5051, open the ignition switch, enter the ABS (03), select the basic set (04), input display group number 03 to activate the test, then the ABS and ASR/ESP lights are lit, and in the fault memory will store “ 01468” fault code;

(2), disconnect the diagnostic instrument VAS5051, start the engine, step down the brake pedal force (pressure about 3500kPa) until the ASR/ESP alarm lamp K86 is extinguished, and the calibration is completed at this time.

(3) the running time is about 5S, the yaw rate is at least 10 s, and the vehicle speed is 15 to 20km/h, and the turning radius is 10 to 12m curve. At this point, ABS, EDS, ASR, and ESP are not working.

After the road test is completed, the ABS and ESP lights go out, indicating that the system is normal. If the two is not extinguished, the fault storage and the failure should be read and then the road test is then carried out. If the road test is discontinued, the ABS and the ESP alarm lights are still lit.

3, lateral acceleration sensor G200 zero balance.

1. Park the car on the horizontal plane, connect VAG1551 or VAS5051 to the 03 address.
Choose login 11, confirm by Q key, enter the login password 40168, and then press the Q key to confirm.
The basic function of setting 04, press Q to confirm, and then enter the unit number 063, then press the Q button to confirm, ABS warning lights flashing;
4. Choose exit function 06. Press Q button to confirm that ABS and ESP alarm lights are about 2S.
5.

if it is shown that the function cannot be executed, it means that the login is incorrect. If the display is basically closed, explain the tolerance beyond zero balance. Read the 08 data flow (-1.5 to 1.5 when the 004 channel second display area is still, the steering wheel to the stop, the left / right turn at 20km speed, the measured value should be increased evenly) and the fault memory. And then again.

zero point balance of.4 and brake pressure sensor G201

The operating methods and steps are as follows:
Don't step on the brake pedal, connect VAG1551 or VAS5051 to the 03 address.
2. Select 08 functions to read data stream and input 005 channels to observe whether the first display area is -7 to 7bar (1bar=100kPa).
Choose login 11, confirm by Q key, enter the login password 40168, then press the Q key to confirm.
The basic setting function 04, press Q to confirm, and then enter the unit number 066, then press the Q button to confirm, ABS warning lights flashing;
5. Choose exit function 06. Press Q button to confirm that ABS and ESP alarm lights are about 2S.
if it is shown that the function cannot be executed, it means that the login is incorrect. If the display is basically closed, explain the tolerance beyond zero balance. We need to read 08 data blocks (005 channels) and fault memory, then reset them.

5, control unit coding

after changing the ESP control unit J104 or the steering wheel angle sensor G85, we must re code the ESP system. The steps of the encoding are as follows:
(1) connect the diagnostic instrument VAS5051, turn on the ignition switch, enter the ABS system (03), select logon (11), enter the login password.
(2) select control unit coding function (07) and input control unit coding.
(3) initialize and calibrate the steering wheel angle sensor, and carry out road test and system test for ESP.

6, read the data stream

A special diagnostic instrument VAG1552 or VAS5051 can be used to read the data of the system, and it can be used to judge the working state of the system according to the data and to analyze the normal work of each sensor. At this time, we should enter the “ 03” address, select “ 08” function, input the corresponding channel number to read the corresponding data. The data flow is shown in Table 1.

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