Failure phenomenon: a 2003 annual BMW E66 730Li sedan, mileage 79000 km. It says users, start the car every morning difficult, unable to operate the starter when starting, starting the day after reluctantly normal use, but the next morning starting difficulties fault will occur.
Check Analysis: The maintenance experience, the vehicle start failure apparently difficult due to battery power loss caused. Use GT1 fault diagnostic examination, it was found that the control unit of the vehicle in a plurality of records are stored on the low voltage fault, but the fault does not exist in the current display. In general, the common cause of battery power loss of the following two points.
Cause
(1) vehicles. For example: long-term parking vehicles or without frequent short distances; engine stall, the multimedia system or lighting system in use for a long time.
Cause
(2) of the vehicle itself. For example, the generator can not generate normal or battery failure; normal vehicle can not sleep, sleep current is too high and the system is frequently wake up.
FIG 1
binding characteristics of the car failure, the reason of the use of the first rule of the vehicle, and because the vehicle barely started after one day of use are relatively normal , so the possibility of the battery and the generator failed basically be ruled out, the most likely cause is that the sleep current is too large or the vehicle can not sleep properly. Sleep next vehicle inspection current is normal, off all electrical appliances and the vehicle door, when the current through the discharge clamp sleep vehicle fault diagnostic observation of GT1, After about 30 min, the failure diagnostic displays sleep current GT1 4.96 A (FIG. 1), the vehicle clearly sleep current is too large, or may be a vehicle that did not enter the sleep state. On the BMW cars, the control unit of each system there are dozens, if the vehicle can not go to sleep in accordance with the design requirements under certain circumstances, will result in excessive battery discharge and loss of electricity. Although BMW cars of various models due to the different configuration requirements for sleep are not the same, but one thing is the same, that is no more than a maximum sleep current of 80 mA. Sleep in several stages to complete the vehicle (FIG. 2), a first stage mdash; mdash; terminal 15 is closed,The second stage mdash; mdash; closed terminal R, the third stage mdash; mdash; lock vehicle insurance, the fourth stage mdash; mdash; sleep start bus, fifth stage mdash; mdash; appliances off after 8 min, the six-stage mdash; mdash; bus 30B closed end. When the vehicle is equipped with a heating system and a parking telephone, enter the sleep total of 60 min, none of these devices is 30 min, turn off the system bus according to the bus terminal end state ldquo; rdquo appliances; (e.g. reading lights and lighting mirror ). When the insured vehicle is locked, it will shut down immediately associated with electrical appliances. When the end state in all the other bus, the bus continues to run off the end 8 min ldquo; ;, rdquo performed by the electrical control module footwell. If the 60 min after the bus is still enabled after the vehicle stops running, the bus terminal Rldquo; Close rdquo; after the vehicle will not be able to enter sleep mode.
FIG. 2
Figure 3
As can be seen from the characteristic graph dormant, in the fourth stage, the current is reduced to 200 mA only be the beginning of sleep, then current gradually decreases until reduced to a predetermined value range of 80 mA. Battery discharge current measured by the fault diagnostic GT1 is 4.96 A, the vehicle does not enter a sleep state described. At this observation car, the remote controller found keyway and ldquo; START STOPrdquo; illumination lamp (FIG. 3) and the seat adjustment switch light remains on, indicating that the vehicle bus has been enabled button. Under normal circumstances, the remote control key is withdrawn by the remote control key hole, within 3 min after the door locking remote control key hole and ldquo; START STOPrdquo; button illumination lights off automatically, 5 ~ 16 min electric lamp will turn off the seat , will switch on the lights will go out, then the vehicle gradually into hibernation. The key now is to find a trigger signal which enables the bus system has been enabled. For this failure, the most simple method is to use a process of elimination, combined with previous experience disconnection controlling unit individually doubt, then ViewRemote control and observation keyway ldquo; START STOPrdquo; illuminated indicator button 3 min, after (FIG. 4) Disconnect the right front door control unit, less than 3 min each associated lamp went out, and then observe the case GT1 the measured sleep current 0.12 a, indicating that the vehicle has entered the sleep state.
Figure 4
troubleshooting: After replacing the right front door control unit, returning the tracking vehicle start failure determination difficult excluded.
reviewed: battery power loss Symptom BMW models are frequently encountered, many times, since the vehicle can not enter hibernation caused by excessive discharge currents caused. For such failure by exclusion exclusion filter, or in a regular order, first to exclude the device after the installation of the vehicle (e.g., navigation, electronic eye alarm equipment), followed by the communications device checks recreational vehicles ( the audio system, telephone, etc.), followed by the respective door control unit and other electrical equipment, and so on until you find the point of failure. Disconnect module is determined only when a fault or electrical connection terminals, then to observe the changes in sleep current, to exclude this failure is progressive discovery opened first passenger-side door control unit TMBFT terminal connection failure of the entire right front door .
(Zhou)