Energy Diagnosis

Energy Diagnosis

Energy Diagnosis
A breakdown due to a drained battery or problems in the vehicle energy system can have a wide range of causes which, in most cases, are not caused by the battery itself. For this reason, replacing the battery will only rarely provide a sustained solution to the problem. The energy diagnosis procedure helps find the cause of the problem.

Result of the energy diagnosis
The procedure reads all the necessary data from the corresponding control units (see below). After evaluating this data, it displays the following information:
- Conspicuous information: this information is only displayed if there was a problem in the vehicle energy system. The number of information items varies.
This information includes the possible causes of a flat battery or a vehicle electrical system fault. Look at the list of possible fault causes, then select the number of the relevant causes in order to bring up detailed information, instructions and the associated diagnosis codes. If there are several possible fault causes, they are listed in order of the kilometer reading at which they occurred most recent first).
For example: the vehicle does not 'go to sleep' (sleep inhibitor); the vehicle is wakened time and again; the side lights were switched on for too long, etc.
- Standard information: this information can always be displayed (evaluation of closed-circuit current monitoring, information about battery such as battery states of charge over last 5 days, driving profile, stationary profile).

On the basis of this information, it can then be decided what the real cause of the fault is.

Overview of possible causes
A breakdown due to a drained battery or a problem in the vehicle energy system is not necessarily the result of a faulty battery. The various causes for discharge of the battery can be placed in two main categories:
- Vehicle faults:
- Vehicle does not assume sleep mode.
- The vehicle keeps being woken up.
- Excessive closed-circuit current.
- Faulty alternator (poor charge balance)
- Faulty battery.
- Unfavorable customer behavior:
- Side lights, parking light or hazard warning flashers were switched on for too long.
- Terminal R or Terminal 15 switched on for too long
- Long immobilization period.
- Unfavorable driving profile (short-distance driving).
- Frequent use of auxiliary consumers or use of auxiliary consumers for a longer period increased power consumption at a standstill).

Data from the vehicle that is read and evaluated
For energy diagnosis, the evaluated data in the vehicle is not changed.The energy diagnosis can be run a number of times and normally always provides the same result.
The energy diagnosis normally provides the same result after repairs, as the data is still present in the vehicle. The partial wakeup signal registration has only been deleted from the energy history memory if a wakeup signal analysis has been carried out. Even after deleting the fault memory, the data from the energy history memory is still stored. However, at the latest when the energy history memory is overwritten with new data, the repaired fault cause is no longer displayed as result of the energy diagnosis.

This data in detail:
- Energy history memory in the JBE (Junction Box Electronics)
The energy history memory (NB: do not confuse with the history memory for fault entries) stores various bits of information that can assist in establishing the cause of problems with the vehicle energy system.
The stored information of the energy history memory in detail:
- The maximum number of wakings within an off-load phase (terminal R off) within the last 5 weeks
- The last 5 control units that prevented the vehicle from going to sleep (with frequency and last kilometer reading of each event)
- The driving profile of the last 5 weeks
The driving profile is stored in the energy history memory with 6 data records. Each data record contains the following information: Starting time of record the data record, distance travelled in km during recording, number of journeys in different ranges.
A new data record is started as soon as the time difference between the current time and starting time of recording of the current data record is greater than 7 days. This means the time span of the evaluation is usually approx. 35 days if the vehicle was not immobilized for a longer period without being wakened.
When all 6 data records in the data memory are full, the oldest data record is overwritten.
- The last 50 CAN messages that woke the K-CAN bus (with kilometer reading of each event)
- Fault code memory in the JBE
The causes of a power-down command or reset or cutoff of terminal 30g-f are stored in the JBE. There are the following fault cases:
- The battery reached the starting capability limit at terminal R off.
- The vehicle is not yet in the idle state 10 minutes after cutoff of terminal 30g.
- The vehicle was awakened unexpectedly more than 20 times after cutoff of terminal 30g.
- Diagnosis requests of the DME/DDE
The DME/DDE stores various data that is used for the energy diagnosis:
- The last 32 cycles of the closed-circuit current monitoring or the standby current histogram are stored
- The last registered battery replacement
- The state of charge of the battery in the last 5 days
- The kilometer readings of the last 5 days
- The auxiliary consumer units switched on during the last 32 cycles: for example, light or independent heating.
- Fault memory in the DME/DDE
The DME/DDE stores a fault entry in the event of a standby current fault and total battery discharge.
- Fault memory in FRM (footwell module)
The FRM is responsible for control of the lights. At terminal R off, the FRM switches the side lights or parking light off if the voltage falls below approx. 11 V. On cutoff, a fault entry is stored. At undervoltage, the LM stores a fault entry. The environment related conditions can be used to determine whether terminal R, terminal 15 or a statutory consumer unit (e.g. light or hazard warning lights) was switched on.