The new function of automatic engine start-stop (MSA) is a fundamental component of the CO2 measure package. This function then ensures an automated shutdown of the engine while the vehicle is being driven if the vehicle comes to a standstill and some essential vehicle conditions (outside temperature in a certain range, brake partial vacuum adequate, clutch not pressed [only on manual transmission vehicles], gear selector switch in off position [only on manual transmission vehicles], etc...) are met to enable the shutdown. There are approximately twenty of these vehicle conditions (so-called shutdown inhibitors).
This function achieves a statistical reduction in the time the engine runs during vehicle operation. This leads to a reduction in the fuel consumption and a reduction of the CO2 emissions. Independently of this, valid legal emissions standards naturally still apply.
Sample scenario: switching off the engine at a standstill at a red traffic light or in stop-and-go traffic.
The automatic new start of the engine is also automatic as soon as the clutch is pressed again [only on manual transmission vehicles] or the brake that holds the vehicle at a standstill is released [only on automatic transmission vehicles].
Important!
The fully automatic switch-on of the engine on MSA vehicles can also occur when the driver performs no action at all. Customer annoyance and customer complaints are not based on a malfunction - this is planned! Situations in which the engine starts fully automatically without any action on the part of the driver are for example:
After every engine start, the function is automatically active and on stand-by. The MSA button (centre console switching centre) can be used to deactivate the function manually until the next terminal change. Pressing the button is confirmed by an LED lighting up. Permanent deactivation of the function is only permitted in extreme exceptional situations (encoding: MSA button, memory function of the IHKA). During the diagnosis sessions, the MSA function is temporarily deactivated for safety reasons (that means until the next terminal change) to prevent the possibility of an automatic engine start during work in the engine compartment. The status of a temporary deactivation can always be read in the control-module functions by means of <detection of deactivation MSA>. Furthermore, the state of the detection / non-detection of an MSA vehicle can be read out in the control-module functions by means of <Check installation of MSA>.
Important!
For reasons of personal safety, it must always be conscientiously determined that the engine start-stop function has been disabled before work in the engine compartment!
The MSA stop is prevented if required due to environmental influences and engine operating values. Examples: cold engine, engine in start phase, battery condition not optimal, air-conditioning / heating output requirements, etc.
The software-internal operating strategy of the MSA function controls the following actions:
The driver receives information on the current status by means of corresponding messages in the display of the instrument cluster.
Current EAs, EVs, AAs, AVs and deactivators as well as general status information can be read out using the service function <System check MSA>. Reading out a history of the last saved shutdown inhibitors is possible by means of the service function <Read AV memory>. This enables a check of past customer complaints.
The MSA function meant that two new sensors were required in the vehicle: the transmission zero gear sensor and the brake partial vacuum sensor. The zero gear sensor enables detection of the neutral position of the manual gear selection switch (only in the neutral position can automated switch-off take place!). The brake partial vacuum sensor enables the current partial vacuum to be determined, as with insufficient partial vacuum an automated shutdown of the engine could represent a safety risk.
The following test modules exist to check the components:
Special points to be observed on diagnosis of the system:
Note 1:
The transmission zero gear sensor component may only be replaced in line with the instructions in the service function <Learn/write zero gear sensor>, as without correct fitting of the sensor the functionality is inactive / faulty. Furthermore, this service function must be run after programming the engine management system, as according to the current implementation the learning values are saved in volatile form in the engine management system. In future, non-volatile storage is planned (the learning routine is then no longer required).
Note 2:
The detailed networking of the function with power management means that initialization by the power management / a closed-circuit current measurement is necessary after disconnecting the battery. This closed-circuit current measurement takes place in an approx. 6-hour cycle (e.g. closed-circuit current measurement ”overnight”), during which the vehicle must not be wakened. In this time, the MSA function is inactive. The customer is to be notified of this when the vehicle is handed over. The MSA function switches back automatically to active as soon as the necessary routine have been completed successfully. A rapid learning routine is possible by means of .... The value learned in the rapid learning routine is volatile.
The following four function / operating modes are indicated by instrument cluster messages:
The CC messages appear when system faults (with or without necessary component replacement) are active or software-related deactivations have taken place. Corresponding reading options are available through the service functions <System check MSA> as well as <Read AV memory>. Other service functions serve as additional plausibility checks and checks of the function characteristics (exception: learn / write zero gear sensor).
Deployment of the new function will take place for the first time on the following dates:
Deployment will initially only be in manual transmission vehicles.