Energy Diagnosis
Energy Diagnosis
Unfavorable customer behavior with vehicle faults is a possible cause of breakdowns due to a depleted battery. In detail, the following individual causes can be determined:
Vehicle does not "go to sleep"
If the vehicle does not reach the rest state after terminal R Off, i.e. the bus systems remain active, the causing control unit is normally determined by the energy diagnosis.The troubleshooting must be continued in the peripherals (e.g. defective sensor or switch) of each control unit. If no fault is determined, renew the control unit. If a number of control units on the PT CAN bus are entered as cause in the energy history memory at the same kilometer reading, the wake-up line should be checked:
- Short circuit to earth or positive
- Loose contact
- First, check the connections of the wake-up line on the IBS, CAS and JBE
Attention:
Operation by the customer can also lead to an entry in some control units: e.g. listening to the radio with terminal R OFF leads to the registration of the headunit (M-ASK or CHAMP with the same kilometer reading as cause in the energy history memory.
Operation of the rear entertainment system by the customer at
Vehicle keeps being woken up
If the vehicle is wakened time and again, the maximum number of wakings in an off-load phase (terminal R OFF) for the last 5 weeks in each case and the IDs of the last 50 waking messages of the K-CAN are determined by the energy diagnosis. The causing control unit is normally determined by the energy diagnosis.If it was possible to determine the waking control unit, troubleshooting must then be continued in the peripherals (e.g. defective sensor or switch, loose contact) of the control unit. If no fault is determined, the control unit must be renewed.
NOTE: In exceptional cases, it is possible that the result "Vehicle keeps being woken up" is generated by unfavorable customer behavior, e.g. frequently waking the vehicle at terminal R OFF by opening and closing the tailgate or doors.
Excessive standby current
The result "Excessive standby current" means that the vehicle, occasionally at least, has had a standby current greater than 80 mA. Here, the vehicle was in the rest state, that is, the bus systems were inactive. A possible cause of this could be defective control units. As troubleshooting, run a standby current measurement and identify possible causes by disconnecting fuses or disconnecting the corresponding control units step by step.
Battery or alternator defective
Even though the battery was not the cause of the complaint, it might have been damaged beforehand due to total discharge for a longer period. For this reason, check the battery condition if you suspect that the battery might have been damaged beforehand.
If there is a suspicion that the alternator is defective, it must be determined whether the DME/DDE has relevant fault entries. Fault entries with regard to the IBS must also be taken into account.
If the vehicle comes to a standstill and will not start during or shortly after a journey, the cause probably lies in the charge balance of the alternator. A requirement here is that the charged battery was still able to deliver adequate current for the starting operation.