Operational strategy: MSA enabled or deactivated
This function activates automatically and then remains in readiness after each engine start. The function can be manually deactivated until the next change of status at the power-supply terminal using the MSA button. When the button is depressed an LED remains lit to signal deactivation.
During diagnosis sessions the MSA is temporarily deactivated owing to safety considerations (remains deactivated until next change in terminal power status). This is to avoid a possible automatic engine start while service work is being performed in the engine compartment. The temporary deactivation status remains constantly visible as "MSA deactivation detected" in the control unit functions. If the control unit functions fail to recognize a vehicle with MSA this is visible as "MSA installation check" and/or "MSA code status".
To ensure personal safety it is absolutely vital that personnel remain consistently conscientious and always confirm that the automatic engine start/stop function has been deactivated before starting work in the engine compartment!
Switch-off request:
| Condition | R55, R56 | E8x, E9x | N43 only Comfort stop preparation |
|---|---|---|---|
| Driving speed less than 3 km/h | x | x | |
| Engine speed below threshold | x | x | |
| Minimum speed has been reached at least one time | x | x | x |
| No gear engaged | x | x | x |
| Clutch not pressed | x | x | |
| Steering wheel not moved | x |
Comfort Stop relies on reduced charge density to prevent the engine from shaking. The Comfort Stop function discharges the air from the intake manifold/plenum chamber (engine continues running for 1 second).
Switch-off prevention:
| Condition | E8x, E9x, R55, R56 | N43 only Comfort Stop |
|---|---|---|
| Switch-off disabled as operational strategy (transverse lockout) | x | x |
| Adaptive switch-off disabled | x | x |
| Engine fault | x | x |
| Switch-off disabled by power management | x | x |
| Carbon canister too full | x | x |
| Brake vacuum too low | x | |
| Catalytic converter temperature too low | N43 only | |
| Engine temperature too low | x | x |
| Outside temperature outside window of operation | x | x |
| Tank fuel level is low | N43 only | |
| time window closed (at least one switch-off prevention factor remains active for too long during the attempted stop) | x | x |
| Diesel particle filter in regeneration | Diesel only | |
| Conditions for Comfort Stop not satisfied | N43 only | |
| Switch-off prevented by A/C request signal | x | x |
| Item | Explanation |
|---|---|
| 1 | The driver brakes until the vehicle comes to a halt. |
| 2 | The driver engages neutral and releases the clutch pedal. |
| 3 | The engine continues to run. A switch-off prevention condition is present. |
Engine start request (simultaneously disables the preparations for Comfort Stop at N43):
| Condition | E8x, E9x, R55, R56 |
|---|---|
| Clutch depressed through more than 10 % of travel range | x |
| Vehicle starting to roll | x |
| Brake partial vacuum inadequate. | x |
| Engine-start request from power management | x |
| Engine-start request from A/C request signal | x |
Engine start prevention:
| Condition | E8x, E9x, R55, R56 |
|---|---|
| No idle or clutch pedal not in end position | x |
| Engine has just stopped: Safety function intended to ensure secure engine shutdown. Otherwise the starter gear could re-engage while the engine is still turning over | x |
All conditions as well as the general status information can be accessed using the "MSA system check" service function. The "Read AV memory" service function can be consulted to view a history of the most recently stored "deactivation disabled" events. This feature can be used to assess earlier customer complaints.