Energy diagnosis

Running the energy diagnosis

A breakdown due to a depleted battery or problems in the vehicle energy system can have a wide variety 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 test module and the displayed help documents assist in finding the cause.

Result of the energy diagnosis

The test module 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 items of information varies.
  For example: the vehicle does not 'go to sleep' (sleep inhibited); the vehicle is wakened time and again; the sidelights were switched on for too long, etc.
  
• Standard information: This information can always be displayed (evaluation of closed-circuit current monitoring, battery charge statuses and other information on the battery, 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 depleted battery or a problem in the vehicle energy system is not necessarily the result of a defective battery. However, in some cases the battery can be damaged - no matter what the cause. The various causes can be placed in two main categories:

• Vehicle faults:
  
  • Vehicle does not go to sleep
    (as a rule, cause can be diagnosed).
    
  • Vehicle is continuously wakened
    (cause cannot be precisely diagnosed).
    
  • Excessive closed-circuit current although vehicle asleep
    (cause cannot be precisely diagnosed)
    
  • Defective alternator: the battery is not charged properly while the vehicle is being driven.
    
  • Defective battery.
    (hard to diagnose)
    
• Unfavourable customer behaviour:
  
  • Sidelights, parking light or hazard warning lights were switched on for too long.
    
  • Terminal R or terminal 15 was switched on for too long.
    
  • Long immobilisation period.
    
  • Unfavourable driving profile (frequent short distances).
    

Data from the vehicle that is read and evaluated

In the energy diagnosis, the evaluated data is not changed in the vehicle until a quick delete has been carried out.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.

This data in detail:

• Energy history memory in the SGM-ZGM (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 information that can help in searching for the cause of problems in the vehicle energy system. 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-ZGM is in the idle state at the moment of the wake-up message.
    
• Fault code memory in the PM (power module)
  Fault entries are stored in the PM when terminals 30 U and terminal 30 B are disconnected from the battery. For each disconnection reason of the PM, there is a separate fault code memory entry. In addition, in the case of undervoltage, a fault code memory entry with important environment-related conditions is stored. The following fault entries are evaluated by the energy diagnosis:
  
  • Reset or shutdown of terminal 30 U and terminal 30 B due to excessive closed-circuit current
    Ambient condition: level of the closed-circuit current
    (disconnected by PM even if the vehicle does not go to sleep)
    
  • Undervoltage
    Environmental condition: Status terminal R, status terminal 15, status whether a statutory consumer unit was switched on (e.g. light or hazard warning lights)
    
• Diagnosis request to the PM (power module)
  The PM stores various diagnosis data that is used for the energy diagnosis:
  
  • The last registered battery replacement
    
  • The state of charge of the battery in the last 9 days
    
  • The kilometre readings of the last 9 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 sidelights or parking light off if the voltage falls below approx. 11 Volts. On cutoff, a fault code memory entry is stored.
  At undervoltage, the LM stores a fault code memory 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.