a new Shanghai GM Buick LaCrosse 3.0 L sedan, the car dashboard users reflect the sometimes show ldquo; Please suspension system overhaul rdquo; tips.
After receiving the car, after careful examination, the vehicle may be determined not made any modifications and variations. Historical failure; and I connected to the vehicle fault diagnostic detection, the device shows ldquo; C0600mdash; mdash; right front acceleration sensor circuit overvoltage / open rdquo.
FIG 1
FIG. 2
For maintenance vehicle electronic control suspension system failure, the need to control the suspension system of the car electronics (Figure 1) an understanding of control theory, for the first electronically controlled suspension system of the car for a brief introduction. Vehicle electronic control suspension system 4 are controlled damping of the shock absorber to control the ride comfort of the vehicle. Changes in the damper can be accomplished within a few milliseconds, the suspension characteristics may change over time or when the motion mode drive mode is activated. An electronic suspension control system comprises a suspension control unit, a vertical acceleration sensor housing 3 (FIG. 2, FIG. 3), two front wheels and four vertical acceleration sensors integrated in the damper damper actuator. Operation of the suspension control unit is a signal acquisition speed, steering wheel position, engine torque, brake pressure and the front housing and the vertical acceleration, the damping force of the damper individually controlled size, so that the maximum possible operating conditions enhance vehicle ride comfort and comfort within range.
Figure 3
The suspension control system function and the control unit detects a fault. The suspension control unit is directly connected to the vertical acceleration sensor, the electronic suspension control unit or a serial data line and the other system receives an input signal, a variable current input to each of the damper actuators. Suspension control unit are provided a common reference voltage of 5 V and the grounding circuit 5 to the vertical acceleration sensor, a vertical acceleration sensor provides a signal of 0.5 ~ 4.5 V to the suspension control unit. Three vertical acceleration sensors are located in the housing front left, right and rear sides, the two front wheels vertical acceleration sensor is located in the strut. VibrationActuator integrated in the shock absorber. An electronic suspension control system using a proportional valve control actuator external channel, performed by the current control regulation, the current consumption is 0 ~ 1.8 A. Actuator response to a suspension instruction of the control unit within a few milliseconds.
no electronic suspension control system failure indicator, but may be used in place of the dashboard instrument cluster display implemented. When the suspension control unit detects a failure, it sets the corresponding fault code and sends the information to the instrument cluster through a serial data line, whereby the meter will display ldquo; Please repair suspension rdquo ;. The suspension control unit can store the fault code as the current or historical diagnostic code. Most electronic suspension control system failure information and displays the fault code is provided on the dashboard instrument cluster. As long as there is a fault code, data will be displayed. The suspension control unit using ignition cycles diagnostic program, even if the fault condition no longer exists, the system will still maintain the operation has taken until the ignition switch to the OFF position. If no fault exists, the fault code stored fault code history, after 41 consecutive ignition cycles without failure, the fault code is cleared.
After receiving the vehicle, the author of the fault code after recording is performed an operation to clear the fault code, the fault code is found to be cleared. After road test found that failure to reproduce, the instrument panel display ldquo; suspension system maintenance request rdquo; tips. I decided to start with the fault code to start. The tips of the maintenance manual, a right front acceleration sensor signal when a voltage lower than 0.5 V and duration 1.5 s, the system will record the fault C0600. No abnormal maintenance personnel check the line, based on past experience in the maintenance, they determined that the suspension electronic control unit internal fault, then replace the electronic suspension control unit (FIG. 4). But after test driving a period of time the fault occurs again, is it just put the electronic suspension control unit again damaged? Or are there other reasons? Then they replaced the right front vertical acceleration sensor, the test results are still disappointing. Line, the sensor and the control unit are normal, but the fault still exists, the maintenance work stalled.
Figure 4
Later, the author involved in car repair faults. In the understanding of the repair process, we first made contact with the user, and it inquired about the failure. In IntoWhen families understand the situation, we got an important message, that is, the probability of failure of the vehicle when turning right large angle is relatively large. At this point I carefully reviewed the troubleshooting process of the car, and did not think of where there are any omissions or unreasonable. So carefully have an impact on what part of the electronic control suspension system when the vehicle is turning right at a large angle observed. Close examination revealed that only the line sensor and is connected on the vehicle body with a displacement of the shock absorber, but has measured the harness is intact. But it still decided to re-measure the entire system line. Accordance with the principles from simple to complex, the author of the first measuring sensor and the connecting lines on the damper body passageway intact. When the analog I harness this angle the steering operation, the line circuit is found connected (FIG. 5).
5
So why is this car harnesses can cause this failure happen? When the vehicle is traveling straight or normal small steering angle, since the wiring harness compare relaxation, will not be stretched; when a large steering angle, twist the wire harness comparatively large line by tensile deformation, not good due to the installation, a long time it appeared disconnection.
After replace the wiring harness, troubleshooting.
Summary: For the measurement of such fault lines, the method using a lot of maintenance personnel is not correct, incorrect detection method is to measure the line straightened wire harness shaking or attention during the measurement. If the inspection can be performed in the correct detection method, a lot of line fault will be more likely to be found.
(Xu Guojia)