a domestic car Chrysler 300C 2.7 L, equipped 42RLE type 4-speed automatic transmission, the user reflect the car dashboard ESP fault warning light, when the vehicle is turning on a wet road surface, occasional slight drift phenomenon.
The description of the user, we first detection and a simple road test, found traction control, ESP and BAS fault warning light, ESP switch does not work, there is indeed a slight rejection sharp turn road test tails, indicating that the car had lost the ESP system.
want to repair the fault of the car, we must understand the structure and principles of the ESP system control vehicle equipment. The main role of the car equipment ESP (electronic stability program) is to prevent the vehicle from skidding when cornering, resulting in loss of control. ESP system equipment in the vehicle, the dynamic sensor and the sensor signal lateral deviation rate sensor is transmitted to the ABM (anti-lock brake control unit) via a bus CAN-C, while the SAS (steering angle sensor) the steering angle signal passed SCM (steering electronic control unit), then to the ABM, PCM and FCM through the bus CAN-C, thereby controlling the braking and engine power output of 4, and then FCM information transmitted via the bus CAN-B to a CCN (instrument cluster). The car as relevant network system topology (FIG. 1).
FIG 1
After understanding the principles of the vehicle control ESP system, the fault can be analyzed systematically car. First dedicated connection Chrysler 300C sedan vehicle fault diagnostic apparatus for the detection, the device shows the presence of two current fault in the ABS system code ldquo; U1003mdash; mdash; ESP CAN C bus operation, U0125mdash; mdash; lost communication with the dynamic sensor rdquo ;. Since these two fault codes are current fault can not be deleted. Now maintenance manuals, maintenance manual prompt fault point these two fault codes includes ESP wire harness, the terminal and connector is damaged, the dynamic sensor high data link short circuit to ground, a voltage short or open, the dynamic sensor low data link circuit short to ground, a short circuit or open circuit voltage, the dynamic internal sensorFault, and antilock brake control means internal fault. Then the author uses to enter ABS control failure diagnostic system looks at the relevant dynamic data flow, contrast can be determined by careful observation, the steering angle data is normal, the normal braking pressure variation, lateral -0.0048 sensor output is no change (normal is 0.028 ~ 0.168 ), the output of the displacement sensor 0deg; no change (normal is 1.3 ~ 5.7deg;), a normal wheel speed variation, are completely normal engine operating data based on the inspection result, a cause of the malfunction for further analysis. Lateral offset of sensors and sensor are integrated in a dynamic sensor, since the two sensor data has not changed, the line is likely to be a dynamic sensor, the sensor itself and the dynamic internal fault ABS control unit.
FIG. 2
According to the circuit diagram (FIG. 2), I decided to first measure the power and ground dynamic sensor is normal, then the ABS control unit and a dynamic sensor connector disconnected. Now the circuit diagram can be seen, the ABS control unit 6 to foot pin for dynamic sensor 3 feed line, the ABS control unit 24 to pin No. 5 pin dynamic sensor ground line ground line, a multimeter ABS control unit of the power supply, Ground and associated line connections are normal. Then the data communication line dynamic sensor is normal? So we measured the first CAN-C low dynamic sensor data lines, which have not found a case ground or short to power; When I measured CAN-C + high data line, the line was found to be short-circuited. At this point the fault has been located, the dynamic sensor to check the ABS control line between the CAN-C + cells found in the next line dynamic sensor fixing bolt has been worn.
After the repair worn lines connecting all the disconnected connector, with the diagnostic trouble code is read, then the fault code has a historic fault codes, may be cleared. After using a fault diagnostic trouble codes cleared, find the start of the vehicle, ESP warning light off, road test data is read ESP system, completely normal. So far, troubleshooting.
Summary: As the dynamic sensor CAN-C + is shorted to ground, resulting in the incoming signal is not dynamic sensor ABS control unit, cause the ESP system function failure, failure alarmAdvertisement lights. For ESP system failure warning light is lit, it should be clear control principle ESP system, which system has associated therewith. In particular fault with the bus, the bus must know the principles of troubleshooting methods and bus communication. Then follow the troubleshooting fault code read by the failure diagnostic view data flow occurs in the system is within the normal range, then according to the meaning of the error code, referring to the circuit diagram and related maintenance manual for repair, find the point of failure. In the process of the troubleshooting, to try to make from simple to complex, step by step, and to avoid duplication check.
(Chenghuai Yu)