Automatic engine start/stop MSA System Service.

General information
The MSA only works when certain requirements are met. In the event of customer complaints, always check these requirements.

Automatic shut-down at terminal 15 as of 03/2007 in vehicles with automatic engine start-stop function (MSA - optional extra 1CC).
Opening or closing the driver door automatically switches off terminal 15 via the signal from the door contact.
By subsequently pressing the START-STOP button, terminal 15 can be switched on again permanently.

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 and/or 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.

Be sure to comply with preventative safety measures for work on MSA vehicles.
Before working on the engine, always switch off the MSA functionality to prevent the engine starting automatically while working in the engine compartment.

In general, stored faults of the MSA system deactivate the automatic engine start-stop.

MSA and power management
The MSA function is strongly networked with the power management. In the event of a battery replacement, disconnection of the battery or after programming the engine management system, the reference data regarding the battery charge state and battery condition can be lost.
They are only available again after a closed-circuit current measurement of approx. 6 hours (e.g. closed circuit current measurement overnight) in which the vehicle may not be wakened. In this training period, the MSA function is not active.
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 has been completed successfully.

Diagnosis instructions
The following test modules exist to check the components:
· (Zero gear sensor)
· (Brake partial vacuum sensor)
· (Clutch switch)
· (MSA button) (networked with centre console switch centre)
· (Door contact MSA) (networked with FRM)
· (DC/DC converter) (networked with JBE)
· (Power management MSA) (information on the vehicle energy system and the last shutdown inhibitors or switch-on requesters from power management)
The service function (Read AV memory) can be used to read out a history of the last stored shutdown inhibitors.

MSA and power management
The battery status that is calculated in the Advanced Power Management (APM) is a major influencing factor on the MSA. The APM monitors the following measured variables: battery charge state, battery temperature, voltage dip during engine start, power consumption of the switched-on consumer units.
In the event of engine shutdown, excessive power consumption must be avoided. To ensure this, at terminal 15 (On) and engine (OFF) the (APM) disables all large current consumer units or reduces their consumption. The displays remain active.
The following consumer units are affected:
· Rear-window defroster (demister)
· Mirror heating
· Seat heating
· Heater blower (the IHKA is responsible for adaptation of the heater blower).
Shutdown inhibitors
The MSA function is only possible if certain requirements are met. An MSA stop is prevented if environmental influences or vehicle conditions require this.
The following shutdown inhibitors are possible from the perspective of the APM:
· Battery charge state is not plausible.
This can have the following possible causes:
o The intelligent battery sensor (IBS) has been disconnected from the power supply or negative battery terminal. The battery charge state cannot be determined.
o The IBS has a malfunction (e.g. communication fault with DME/DDE).
o There is a sustained closed-circuit current fault and it prevents an open-circuit voltage measurement to determine the battery charge state.
Find the cause of the closed-circuit current fault.
o The vehicle is continuously in operation and did not have an adequately long off-load phase for an open-circuit voltage measurement to determine the battery charge state.
Let the vehicle go to sleep and leave it in the off-load state for at least 1 hour.
o An additional current consumer is directly connected to the battery and leads to a fault in determining the battery charge state by the IBS.
· The battery charge state is too low.
The battery charge state does not correspond to the minimum state of charge required for MSA. The battery must be charged and troubleshooting continues with the test module (Energy diagnosis).
· Battery temperature too high.
The battery temperature is too high to reliably determine the battery charge state.
· Excessive voltage dips during the previous MSA engine start.
The APM continuously monitors the on-board supply voltage and especially during the engine start.
The voltage fell short of a threshold value during the previous MSA engine start.
The battery temperature is too low or the battery is possibly poorly charged: recharge the battery and continue troubleshooting with the test module (Energy diagnosis).
· Power consumption of the switched-on consumer units is too high.
The switched-on current consumers require too much current: MSA stops are not permitted so that the battery can be supported by the alternator.
Switch off large current consumers (e.g. heated rear window, seat heating or heater blower) so that MSA stop is permitted once again.
The current and last four shutdown inhibitors that occurred are saved in the data of the power management.
The power management also saves the last nine shutdown inhibitor types: if a shutdown of inhibitor occurs a number of times in succession, it is only examined once.
Switch-on requesters
The fully automatic switch-on of the engine by MSA can also occur when the driver performs no action at all.
Some vehicle conditions (switch-on requesters) require an immediate MSA engine start without action on the part of the driver.
The following switch-on requesters are possible from the perspective of the APM:
· During the MSA stop, the battery charge state falls short of the state of charge required for the MSA function. The engine is switched on again automatically to improve the charge balance.
The current and last four switch-on requesters that occurred are saved in the data of the power management.

Battery
For vehicles with automatic engine start-stop, an AGM battery must be fitted in all cases and it must be registered after battery replacement using the service function (Register battery replacement) so that the MSA function can work perfectly.
In the event of a battery replacement, disconnection of the battery or after programming the engine management system, the reference data for the battery charge state and battery condition can be lost.
They are only available again after an open-circuit voltage measurement of approx. 6 hours (e.g. off-load phase overnight) in which the vehicle may not be wakened. In this training period, the MSA function is not active (shutdown inhibitor = battery charge state not plausible). 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 routines have been completed successfully.
 

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