a 2006 annual import Chrysler 300C 3.5 L sedan, users reflect the situation in the car suddenly appeared after parking overnight Day 2 morning not normally start.
After receiving the vehicle, the starter operation test found weakness, severe loss of power of the battery was measured. First, the vehicle diagnostic connection failure is detected, the control unit all the vehicles found no fault code memory, each system stream is normal. Then I decided to self-discharge current test vehicle. After closing all appliances, I will remove the key and ignition off, disconnect the battery negative electrode, an ammeter measuring series, when the current reading of 2.9 A, after waiting for 3 min current drops to about 2.1 A, after which no Variety. Under normal circumstances, the normal self-discharge current of the car about 35 mA (when the ignition switch to OFF, and the normal vehicle electrical system current consumption of 0.005 ~ 0.035 A). The self-discharge test results, the vehicle may be determined from the presence of abnormal discharge.
for investigation for such self-discharge check failure, disconnect the fuses one by one general method may be employed and a relay. When it finds the line and the discharge element, once disconnect the corresponding fuse, the self-discharge current is normal. When I the distribution center of the fuse 14 is removed, the self-discharge current is reduced to 0.035 A, normal values. After checking the relevant circuit diagram can be seen, the control unit 14, a fuse (HVAC) to the air conditioner, combination meter (MIC) and the antitheft control unit (the WCM) provides power (FIG. 1), it is necessary to further determine whether the three elements which element or line out of the question.
FIG 1
After the air conditioner control unit I disconnect connector, the fuse will disconnect the plug, the self-discharge current is again measured, the current value does not change, indicating no leakage air conditioner control unit. Disconnect combination meter continues the connector, the self-discharge current of the vehicle and not change down to 1.7 A, although the self-discharge current is reduced, but still not in the normal range. Continue disconnect connector antitheft control unit, when self-discharge current of the vehicle is reduced to 0.035 A, normal values. Is also damaged two elements? Combination meter connected individually disconnect the antitheft control unit, when the self-discharge current of 1.1 ABut I found the driver’s side door latch locks automatically. To further determine whether the problem is a combination meter, we decided to use alternative method of determination. So I found with normal performance car instrument cluster mounted to the vehicle fault is measured. When the anti-theft control unit is not connected, the same as with the previous detection result, self-discharge current of the vehicle is only reduced, but can not restore normal, and only while the instrument cluster of the vehicle antitheft control unit turns off normal will self-discharge current. Alternatively experiment ruled out the combination meter failed, further determines that the fault on the anti-theft system control unit.
2
then the anti-theft control unit damage Why is there such a situation? I find a circuit diagram (FIG. 2, FIG. 3), after careful analysis circuit seen, each door latch driven by combination of instruments, antitheft control unit via the CAN bus signal is transmitted to the instrument cluster. Damage to the control unit the driver side door latch malfunction, so when the measured discharge current should be a combination of a current meter into the closure.
Figure 3
Finally, after the replacement of the car antitheft control unit, troubleshooting test.
Summary: It is noted that after the replacement of the antitheft control unit (the WCM), should also be used for the WCM fault diagnostic, and the ignition key for tire pressure monitoring systems and the corresponding matched set, or it may cause problems or can not start a vehicle tire pressure monitoring system false alarm occurs. Further, when the self-discharge current measured vehicle, the best conditions possible to be measured by the current clamp, in order to avoid locking sound like unnecessary trouble.
(Guozhen Yong)