Description of energy diagnosis

Running the energy diagnosis:

The energy diagnosis is the test module to determine the cause of a flat battery. The energy diagnosis requires that charging the battery via the alternator functions as a general principle. A fault in relation to the alternator can be seen from corresponding fault entries or undervoltage with the engine running.

The energy diagnosis distinguishes only the following faults:

• Battery defective / alternator defective
  (difficult to diagnose)
  
• Vehicle is continuously wakened
  (cause cannot be precisely diagnosed)
  
• Vehicle doe not go to sleep
  (as a rule, cause can be diagnosed)
  
• Excessive closed-circuit current although vehicle asleep
  (cause cannot be precisely diagnosed)
  
• Customer behaviour
  (as a rule, the result when there is no fault in the vehicle)
  The customer behaviour fault can be further distinguished as follows:
  
  • Light or hazard warning lights were switched on
    
  • Terminal R or terminal 15 was switched on
    
  • Unfavourable driving profile
    
  • Long immobilisation period
    

Result of the energy diagnosis:

The energy diagnosis assumes that the vehicle had a flat battery. The 3 most likely fault causes are displayed, insofar as they can be determined. The most likely cause of the fault is in the first position. The individual results are also evaluated according to their information content.

***** - corresponds to very good information content
** - corresponds to medium information content
* - corresponds to very low information content

The energy diagnosis only provides a correct result if the fault code memory has not been deleted since the fault occurred.

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. Even after deleting the fault code 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.

Evaluation of the energy diagnosis:

For analysis of the cause of a flat battery, a variety of diagnosis information is read from the vehicle and evaluated. This information in detail:

• Energy history memory in the SGM-SIM (Safety and Gateway Module)
  The energy history memory (NB: not to be confused with the history memory for fault code memory entries) stores a variety of information regarding bus messages that can help in searching for the cause of a flat battery. The energy history memory consists of 100 entries in a ring memory. If a new entry is stored, the oldest entry is overwritten. A new entry in the energy history memory is stored under one of the following conditions:
  
  • The vehicle is in the idle state and is wakened.
    
  • After 30 minutes terminal R off, at least one control unit prevents the vehicle from going to sleep (a separate entry is made for each control unit)
    
  • The vehicle detects that the starting capability limit of the battery has been reached
    
  • The vehicle detects undervoltage
    
  For each entry, the following information is stored:
  
• • The relative time and kilometre reading of the instrument cluster
    
  • Status of terminal R at the moment of the entry
    
  • For a unit preventing the vehicle from sleeping:
    the control unit that prevented sleeping at the moment of the entry
    
  • When the vehicle is wakened:
    the bus system that wakened at the moment of the entry.
    It cannot be identified which control unit wakened. The reason is that the SGM-SIM is in the idle state at the moment of the wake-up message.
    
  • The after-run time of terminal 30g
    (if a control unit wakes up with terminal 30g switched off, it must be a control unit supplied by terminal 30.)
    
• Fault code memory in the MPM (Micro Power Module)
  The MPM has a bistable relay that controls terminal 30MPM. If the MPM detects a fault, it switches terminal 30MPM off. The reason for the cutoff of terminal 30MPM is stored in the MPM. There are the following fault cases:
  
  • The battery reached the starting capability limit at terminal R off.
    
  • 30 minutes after terminal R off, the vehicle has not yet switched into the idle state.
    
  • The vehicle was wakened unexpectedly at terminal R off more than 30 times.
    
• Diagnosis requests of the DME/DDE
  The DME/DDE stores various data that is used for the energy diagnosis:
  
  • The IBS totals the time in which the closed-circuit current is within a certain range. The are 4 defined closed-circuit current ranges, whereby only the range between 0 - 80 mA is normal.
    
  • The last registered battery replacement
    
  • The state of charge of the battery in the last 5 days
    
  • The kilometre readings of the last 5 days
    
• Fault code memory entries of the LM (Light Module)
  The LM is responsible for control of the lights. At terminal R off, the LM switches the lights off if the voltage falls below approx. 11 Volts. 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.