Case 1
Failure phenomenon: a 2007 annual Shanghai Volkswagen POLO AccFast 1.4 L sedan with automatic transmission, mileage 32000 km, users reflect the ABS warning light lit. User failure scenario is described: three months ago when the mileage of 25,000 km, ABS lamp has been lighted, the replacement of the right front wheel speed sensor, ABS lamp goes out. So normal driving for some time, the recent ABS light and bright. User requirements completely solve the problem.
check analysis: the new POLO sedan version is equipped with Bosch 8.0 ABS system. I VAS5052 connected fault diagnostic, inquiry into the ABS control unit J104 memory failure, find a fault code: 00285 035 mdash; mdash; G45 right front wheel speed sensor signal unreliable. After recording the fault code, clear fault memory, ABS warning lamp is off. VAS5052 connected to road test, reading out the measured values of the wheel speed of the four wheels 001 group. Initially, the four wheels of the same wheel speed rises, but at 35 km / h, right front wheel speed suddenly decreased from 35 km / h to 25 km / h, ABS lamp lights up immediately. Fault code G45 right front wheel speed sensor signal unreliable.
the right front wheel speed sensor just replaced soon, is it a problem with the wiring harness G45? Disconnect the connector J104, the terminal T38 / 6, T38 / 18 of the respective two terminals of the wire harness-side connector J104 G45 connector measurement of normal conduction. Suspected ABS control unit interface circuit corresponding to the right front wheel speed sensor inside the line of the solder joints Weld G45 (with a similar situation), resulting in poor and right front wheel speed signal. Because the car is still under warranty claims period, then changed to a new ABS control unit. The control unit 199 to write the coding, and the job is completed deflated brake line, start the engine, ABS lamp goes out. Road test with less than 100 m, the vehicle speed is 35 km / h, ABS lamp is lit again, the fault code signal is still not reliable G45. 001 of right front wheel speed signal region 2 was observed with the measured value, at 35 km / h or suddenly fell to 25 km / h, it shows the signal G45 is not normal, independent of other portions.
the wheel speedFor the sensor unit outputs a normal wheel speed signal can be controlled to the ABS, to reliably induced magnetic field changes in the vicinity of the wheel ring. If the magnetic field is unstable, the wheel speed sensor can not work properly, you should check the clearance ring and the wheel speed sensor. POLO car wheel bearing ring integrated in the front wheel, right front Remove knuckle, front wheel bearings has been found that the normal position displaced outwardly a distance of about of 2 mm (FIG. 1). Since the gap G45 right front wheel speed sensor and the ring is too large, the sensor output signal distortion, error resulting ABS control unit processes the data signal, the ABS warning lamp lit.
FIG 1
Troubleshooting: service specification by replacing the right front wheel bearings. Start the engine, ABS lamp goes out. Road test was observed in the measured values of the wheel speed of the four wheels 001 groups showed changes in synchronization at different speeds. So far ABS lights lit fault completely ruled out.
reviewed: When you exclude this category faulty sensor signal bad habit of thinking tend to focus only on the inspection of the sensor itself, while ignoring the existence of the sensing objects. This case is precisely for this reason that walking a few detours, and learned this lesson worth pondering.
Case 2
Failure phenomenon: a 2003 annual POLO 1.4 L sedan with automatic transmission, the engine equipped with BCC and 001 four-speed automatic transmission, mileage 146,000 km. Users reflect car idle shake, the EPC lamp is lit, the engine speed is 900 ~ 1 100 r / min ups and downs, depress the accelerator pedal, the engine speed can not be raised immediately.
Table 1
Check Analysis: maintenance staff confirm failure. VAG1552 connection failure diagnostic query engine control unit J220, there are two fault memory fault code: 17961 P1553 035 mdash; mdash; unreliable intake manifold pressure sensor G71 and F96 of the ratio of the altitude sensor; 17912 P1504 035mdash; mdash ; intake manifold leak. Fault code 17912 is in most cases an intake manifold absolute pressure value is greater than 48.0 kPa due. 08 into the set of measurements menu to set a data access code associated with the fault (Table 1). The oxygen sensor signal data has been at a low voltage constant current seen with as lean air-fuel mixture state, indicating the presence intake leak points. The process being checked, the engine suddenly made a similar tape slip ldquo; creak rdquo; crankcase ventilation valve sound, the sound source position to identify, if the right side of the engine, this position is equipped with oil separator, think intake manifold leak doubt exists, identified as howling (FIG. 2) crankcase ventilation valve membrane due to damage. Disconnect and blocked crankcase ventilation valve connected to an intake manifold of the vent hose, howling disappeared, the instrument EPC light is off, the engine steady operation is resumed. Thereby confirming crankcase ventilation valve leakage cause too lean mixture. Fault chain is formed using the following written description: lean-burn rate is too slow rarr; engine speed drops, unstable operation jitter rarr; an intake manifold absolute pressure rise rarr; fuel injection pulse width is increased rarr; mixed gas quality have improved rarr; engine speed increases rarr; throttle motor adjusting seeks the target value reaches an idle rarr; throttle angle at 5 ~ 7deg; repeated changes rarr; engine idle fluctuation rarr; EPC lamp lighting rarr; hard acceleration.
FIG. 2
Solution: Replace the crankcase ventilation oil separator valve, clear the fault, troubleshooting. Read before servicing primary measurement values comparable with the engine idling operation (Table 2), are in line with specification values, to this end Orthogonal maintenance.
Table 2
Case 3
Failure phenomenon: a 2006 annual POLO Jin love 1.4 L automatic hatchback, mileage 32000 km, users reflect the baggage door difficult to open, the rear windshield wiper motor does not work.
Check Analysis: found by maintenance personnel really bad baggage door opening, can be opened when it happens, brake lights will light up. The high mounted stop lamp is not lit, the luggage door can not be opened. After the operation of windshield wiper switch E34, electrical wiperMachine does not operate. Wiper lever pull, lift the load, the motor rotates slowly, the motor described unable to work. The examination result of the analysis, opening the luggage compartment locking doubt V53 motor, the wiper motor on a common grounding point V12 M25 and the brake lights. Now that the circuit diagram, the common grounding point grounding point 53 located on the left side C-pillar baggage door. Open the luggage compartment trim, Discovery grounding point fixing nut 53 is not tightened, the grounding line virtual connection (FIG. 3). It is estimated that due to the rear of the car had an accident, the repair process negligence.
Figure 3
Troubleshooting: Clean and polished 53 grounding point, the fastening nut, troubleshooting.
Figure 4
failure mechanism analysis: anomaly that occurs when failure is how is it? A (FIG. 4), the normal state, the handle is pulled tailgate, E234 switch is closed, the control unit J519 vehicle network recognizes a low level signal. The J519 T6O / 5 12 V voltage output terminal V53 → → → node 98 node 287 → white → Ground line 53 grounding point, the motor operation of the luggage compartment opening, the luggage door is opened. Under a fault condition, since the grounding point nut 53 is not tightened, white, brown as a virtual grounding line contact state. Ground brown white line is closer to the body than the grounding line, when the line is disconnected Ground Ground brown, white grounding line, a current path node J519 → V53 → 98 → node 287 → M25 → brake brake lights lamp M9, M10 → brown → Ground line 53 grounding point. M25 brake lights from the light emitting diode, a light emitting diode element is a voltage type, the operating current required is very small, so when opening the luggage door lights. Current path when the wiper motor V12 → V12 → SBl work 98 node 287 node → → → brake lights and brake lights the M25 M9, M10 → brown → Ground line 53 grounding point. Since the high-resistance after high mounted stop lamp, the operating current of the wiper motor is small, and therefore weak rotation.
Case 4
Failure phenomenon: a 2006 annual POLO AccFast 1.6 L sedan with automatic transmission, mileage 24000 km, in addition to the user to reflect the driver’s side door car, the other carElectric windows can not control.
Figure 5
Analysis Check: After the maintenance personnel to do the basic examination, the front passenger door, rear right, and rear left door power window can not control switch controlled by the driver’s door lifting power window. Pressing the doors own control switch is also invalid. VAS5052 connected fault diagnostic, inquiry system control unit J393 is comfortable, non-fault code memory. Power window control mode and POLO Jin AccFast older cars with different POLO, power window switch status information transmission rate of 20 kb / LIN bus transmission s, the driver-side door of the control unit J386 LIN bus the main control unit (FIG. 5), the remaining three door control unit is a slave unit. The control principle is as follows (the previous row passenger side door power window as an example): LIN bus activated when the ignition switch ON, the power window switch signal E81 is input to the control unit on the driver’s door J386, J386 after transmitting the identification signal to the LIN bus front passenger-side door control unit J387, J387 front passenger-side power window control motor V148 according to the received operation instruction window lift. When operating the front passenger-side power window control switch E107, J387, as the control unit recognizes the input from the switch signal E107, V148 direct control action. Possibility
Figure 6
Because each unit has its own door control protection fuse, door control unit 3 is small while off , so the cause of the malfunction in the power failure can be ruled out. According to the symptom analysis, maximum likelihood problems with the four door control units relevant to the LIN bus. Following this idea, we decided to check the front passenger-side door control unit J387 LIN bus line between the cell and J386 driver door control. Measured with a multimeter harness-side connector J387 T8ak / 3 terminal and the harness-side connector J386 T8aj / 3 terminal of the resistor, infinite display, show the LIN bus between J386 and J387 in the OFF state. A (FIG. 6) can be seen, respectively LIN bus J386 J387, J388 and J389 is connected via T21 / 20 of the connector terminals of the left A-pillar, the connector disengagement was observed, T21 / 20 LIN bus terminals located corroded, broken pins remaining in the corresponding insertion hole (FIG. 7). Since the door portion LIN bus failure, and can not work alone as the remaining three from the door control unit for the control unit, the above-mentioned failure phenomenon occurs.
Figure 7
Troubleshooting: Use A kit replacement harness Mass VAS1978 left A-pillar T21 / 20 terminal wire connector refitted Test All doors power windows, all returned to normal.
(Chenzhong Ze)