Energy Diagnosis

Energy Diagnosis

Unfavourable customer behaviour 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. faulty sensor or switch) of each control unit. If no fault is determined, replace 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 kilometre 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 (if fitted), CAS and JBE

In the case of 1 Series and 3 Series produced before 12/2006 with fitted IBS: If terminal 15 can no longer be switched using the start/stop button or the electric steering lock (ELV) cannot be unlocked, check the installation location of the battery for traces of dampness and examine the fault entries regarding the IBS: The IBS may be faulty due to moisture and keep the wake-up line at high level. In this case, replace the IBS. For vehicles produced after 12/2006, a new water-tight IBS is used.Important. 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 RAD, RAD2 or M-ASK and possibly CID with the same kilometre reading as cause in the energy history memory.

Vehicle keeps being woken up
If the vehicle is wakened time and again, the maximum number of wakings in an rest phase (terminal R OFF) for the last 5 weeks is determined.The causing control unit cannot be determined automatically: Identify the possible cause by disconnecting fuses or disconnecting the corresponding control units step by step. If it was possible to determine the waking control unit, troubleshooting must then be continued in the peripherals (e.g. faulty sensor or switch, loose contact) of the control unit. If no fault is determined, the control unit must be replaced.

NOTE: In exceptional cases, it is possible that the result "Vehicle keeps being woken up" is generated by unfavourable customer behaviour, 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 faulty 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.
Procedure for external standby current measurement: see Service Information number 61039947.

Battery or alternator faulty
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.
See Service Information (SIT)
610702875
If there is a suspicion that the alternator is faulty, 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.