Description And Operation: Operation: Notes
Engine stopping mode with manual gearbox
With the vehicle stationary, the engine (3) stops with the gearbox in neutral (1) and the clutch pedal (2) released. The engine can be stopped at speeds below 7 km/h (4 mph).
Engine restarting mode with manual gearbox
Press the clutch pedal (4) to restart the engine (5).
Engine stopping mode with automatic transmission
The engine (2) stops if the car stops with the brake pedal (1) pressed.
Keeping the engine stopped with automatic transmission
With the brake pedal pressed (1) and the engine at off (2), position the gear lever in N (3) and release the brake pedal (4).
Engine restarting mode with automatic transmission
If the gear lever is in N, place it in any gear position (8); otherwise, release the brake pedal (7) or move the gear lever in a position other than N. The engine starts again (9).
Failed engine stop conditions
- When the vehicle is operating, due to comfort, emission control and safety reasons, the engine may not stop in some conditions, such as:
- Engine still cold.
- Battery not sufficiently charged.
- Windshield wiper at max. speed.
- Particulate filter regeneration in progress (only for diesel engines).
- Driver door not shut.
- Driver seat belt not fastened.
- Reverse engaged (for example parking operation).
- With automatic climate control, if a suitable level of thermal comfort has not yet been reached.
- 4WD low Active.
- Heated windshield active.
In the above case, an informative message is shown on the Instrument Panel Cluster (IPC).
Automatic restarting conditions
- Due to comfort, emission control and safety reasons, the engine can restart automatically without any intervention by the driver, under special conditions, such as:
- Battery not sufficiently charged.
- Low braking system vacuum (for example after the brake pedal has been pressed repeatedly).
- Car moving (for example on roads with a gradient).
- Engine stopped by the S/S for more than three minutes.
With a gear engaged on vehicles equipped with a manual transmission, the automatic restarting of the engine is only permitted by fully depressing the clutch pedal. This operation is requested through a message on the IPC.
If the clutch is not pressed, when three minutes have elapsed since the engine was stopped, the engine can only be restarted using the key.
In the case of an undesired engine stopping as a result of sudden clutch pedal release with gear engaged, if the S/S system is active, the engine can be automatically restarted by fully pressing the clutch pedal or placing the gearbox in neutral.
Safety functions - When the engine is stopped by the S/S system, if the driver releases their seat belt and opens the driver side or passenger side door, the engine can be restarted only using the key.
"Energy saving" function - If, as a result of the engine automatic restarting, the driver does not execute any action on the car for a long time, the S/S system stops the engine once and for all, to prevent fuel consumption. In this case restarting requires the key.
Important
- The car should always be left after the key has been removed or turned to the OFF position.
- Before opening the hood, make sure that the ignition is turned OFF and the key is in the OFF position. It is advisable to remove the key when there are other people in the car.
- When refueling, make sure that the ignition is turned OFF with the key in the OFF position. It is advisable to remove the key when there are other people in the car.
- If you want to make the most of climate comfort, the S/S system can be deactivated to allow continuous operation of the climate control system.
Irregular operation - In the case of malfunction the system is deactivated. The driver is informed about the switching on of the warning light for general failure and, where provided, by the information message and by the icon of system failure on the instrument panel.
The illustration above is a block diagram of the vehicle, divided by area. Each area shows the main components involved in carrying out the S/S function. In particular, the following are highlighted:
- A: white, additional components;
- M-HW: yellow, components with modified hardware or mechanics as compared to those normally present;
- M-HW/SW: orange, components with modified hardware and/or software as compared to those normally present;
- CO: green, components which have not been changed or adapted as compared to the originals.
Key:
- A: added components.
- HW: components with modified hardware.
- HW/SW: components with modified hardware/software.
- CO: Carry Over components (not modified).
HMI area (Human Machine Interface)
- 1: accelerator pedal.
- 2: clutch pedal.
- 3: brake pedal.
- 4: transmission control.
- 5: S/S push-button.
- 6: instrument panel.
PWT area (powertrain)
- 7: accelerator potentiometer.
- 8: clutch sensor.
- 9: brake sensor.
- 10: transmission sensor.
- 11: engine temperature sensor.
- 12: braking system vacuum sensor.
- 13: engine rpm sensor.
- 14: other (handbrake, catalytic converter, etc).
- 15: flywheel.
- 16: engine.
ECM: engine control module (engine control Module)
VEHICLE area
- 17: starter
- 18: generator.
- 19: various loads (heated rear window, windshield wiper, etc.).
- 20: seat belt fastened sensors.
- 21: door sensors.
- 22: outside temperature sensor.
- 23: battery.
- 24: voltage stabilizer for radio and Hi-Fi.
- 25: various electrical loads.
- RRM/ HI-FI: radio receiver/Hi-Fi module.
- IBS: Intelligent Battery Sensor (battery monitor).
- FP: dummy pole.
- NCL: Heating, Ventilation and Air Conditioning (HVAC) module.
- BCM: Body Control Module
Added components (white)
- 5: S/S function activation/deactivation button.
- 10: transmission sensor.
- 12: brake servo vacuum sensor.
- 24: voltage stabilizer for radio and info-telematics supply.
- FP: dummy negative battery pole with wiring.
- IBS: Intelligent Battery Sensor (battery monitor).
Components with modified hardware (yellow)
- 2: clutch pedal with clutch sensor.
- 13: engine rpm sensor.
- 16: engine.
- 15: flywheel.
- 17: starter.
- 18: generator.
- 23: battery.
Components with modified hardware and/or software (orange)
- 6: instrument panel.
- ECM: (Engine Control Module).
- BCM: (Body Control Module).
- NCL: (HVAC Module).
- ABS: (Braking System Control Module)
Carry over components (green)
- 1: accelerator pedal with accelerator sensor.
- 3: brake pedal with brake sensor.
- 11: engine coolant temperature sensor.
- 20: belt sensors.
- 21: door sensors.
- 22: outside temperature sensor.
- 14: other (handbrake, catalytic converter, DPF, heated rear window, windshield wiper, general electrical loads, etc.) RRM: Hi-Fi radio.
S/S activation button
| Pinout | |
|---|---|
| 1 | Ignition-operated power supply |
| 2 | LED control for backlighting |
| 3 | Earth |
| 4 | Switch signal |
| 5 | n.c. |
| 6 | Switch signal |
Sensor for gearbox in neutral:
- The transmission sensor is fitted on the gear lever unit and transmits to the ECM a signal enabling the system to recognize the position of the lever corresponding to the "transmission in neutral" condition.
- The condition of transmission in neutral is essential for the engine automatic starting.
- The transmission sensor generates a PWM signal with a duty cycle between 33% and 67% when the transmission is in neutral.
Vacuum sensor on brake servo - The vacuum sensor on the brake servo informs the system that the vacuum in the circuit is not enough to guarantee efficient braking with the engine off, due to a lack of brake servo intervention. In this case the engine is restarted or is not stopped if it was already running.
The sensor is connected to the ABS module and is closed if the absolute pressure of the circuit is low enough (about 400-500 mbar / 5.8 psi).
Clutch sensor - The clutch sensor S (no. 8 in the block diagram) plays a primary role for the Stop & Start function because, in combination with the transmission sensor, enables the automatic starting of the engine. The sensor is located on the pedal unit. The sensor is rotary type and provides a signal to the ECM whether the pedal is released or pressed and also if the pedal is not fully depressed. In this way the system can recognize the pedal position regardless of where it is in the stroke.
The ECM receives from the clutch pedal sensor a value which can be HIGH (pedal not pressed), MIDDLE (pedal partly pressed), LOW (pedal fully pressed) or ERROR (sensor error).
Fuel pump - When the S/S system is activated, during the engine stopping stages the fuel pump remains active. This guarantees a full fuel delivery system, ready for startup. When the engine does not run for a certain period of time, the pump is turned off.
Voltage stabilizer
- The voltage stabilizer maintains the supply voltage of some devices (the radio receiver in particular) within values which guarantee that the supply voltage is maintained during the engine startup stages.
- The voltage stabilizer consists of an electronic unit directly connected to the battery.
- It is positioned under the dashboard, on the right side.
Operation - With the key at STOP: the T1 relay switch is closed and the device is completely bypassed. In these conditions the battery positive is applied to +30 of the radio and to the entire Hi-Fi system, if present. With the ignition switch ON (+15 present) and during the startup stage (+50 present), the T1 relay switch is opened and the T2 and T3 relay switches are closed. In this way +30 of the battery can pass through the voltage stabilizer because in this condition a voltage drop can cause a temporary audio interruption or the stored channels can be lost.
Diagnosis - The diagnosis is performed through the scan tool to which the diagnosis cable (DIAG) is connected. The fault status is signalled to the scan tool by means of a low digital signal.
Two types of stabilizers are available: 90 W if the car is only equipped with the radio and 180 W if it has both the radio and the Hi-Fi system.
Intelligent Battery Sensor (IBS) and dummy negative pole - The IBS (A) is an electronic unit which informs the BCM of the battery operating conditions. This prevents an engine shutdown in case the charge conditions or health of the battery are inadequate.
The information produced by the IBS and sent to the BCM through the Local Interface Network (LIN) is used for the management of the Start & Stop function to take the battery starting capacity into consideration. In particular, this information is used, in conjunction with other information coming from other vehicle devices/control units, to activate or deactivate the Stop/Start function.
The general concept is that, while the engine is running it should not be stopped automatically if the capacity of the battery is not sufficient to start it and, during an automatic stopping stage, the engine should be restarted if the battery startup capacity becomes too low.
The Stop/Start function is also deactivated if a possible IBS fault does not allow the effective battery status to be determined: an internal error signal is generated in the BCM to this end.
The Stop/Start is primarily managed by the ECM which decides whether to activate/deactivate the Stop/Start taking a great deal of information into consideration, including data coming from the IBS (through the BCM).
The BCM and ECM can also deactivate the Stop/Start function as a result of vehicle conditions not connected to the IBS.
IBS - Operation
- The IBS performs the following measurements:
- Battery voltage (V)
- Battery current (A)
- Battery temperature (°C)
The control unit processes these values and calculates the following parameters expressing the battery status:
- SOC : (State Of Charge) percentage of the battery residual charge as compared to its rated capacity, indicating charge of the battery.
- SOH : (State Of Health) "age" of the battery or, better, percentage of the battery real capacity as compared to the rated capacity. This condition has to be considered because the battery undergoes an irreversible aging process with time, reducing its ability to be fully recharged and therefore the possibility of supplying all the energy it could store when new.
- SOF : (State Of Function) minimum voltage peak that can be reached during the startup stage, in volts.
These parameters identify the starting capacity of the battery.
In the case of insufficient SOC or SOH, the battery might not be able to restart the engine any more. In the case of insufficient SOF, the battery voltage during starting may reach such low values that the standard operating conditions of the various electronic units of the car are no longer guaranteed.
Calibration of the IBS - When the IBS is connected to the power supply for the first time or is reconnected after a service operation, performs a recalibration.
During recalibration, the battery efficiency status (SOC, SOH and SOF) is calculated in a less accurate way and with broader tolerances for a certain period of time during which the IBS must recognize the type of battery it is connected to, its voltage and its efficiency status. During this period, the S/S system may not stop/restart the engine to prevent the risk of an insufficient energy level remaining in the battery.
Whenever the IBS is removed from or connected to the battery or the battery is replaced, when the connections are restored a calibration processes is started to store the battery efficiency status again.
The following table illustrates the calibration process logic.
| Restoring supply | First startup | First period of inactivity > 4 hours and engine startup | 5 time for 8 hours of inactivity, followed by car starting | |
|---|---|---|---|---|
| SOC | Out of range | Out of range | Tolerance OK | Tolerance OK |
| SOF | Out of range | Tolerance OK | Tolerance OK | Tolerance OK |
| SOH | Out of range | Out of range | Out of range | Tolerance OK |
| CALIBRATION | STANDARD OPERATION | |||
When the power supply is restored - all parameters are out of range because the system is not able to determine the battery status yet.
At the first starting - it performs the SOF calibration, considering immediately the minimum voltage already reached at the first starting. The other parameters cannot be taken into account yet.
After a period of inactivity longer than 4 hours and at least a starting cycle - the SOC parameter is also considered, which determines the battery charge status after a certain period of time has elapsed. The state of health - SOH - is not considered yet because it is still necessary to alternate startup cycles and inactivity periods. The real efficiency status of a battery can be determined if also the elapsed operation time is considered.
After 5 inactivity periods of at least 8 hours, combined with a series of starting attempts - the cycle ends and the SOH parameter is acquired and stored
If the IBS does not recognize the values of the above mentioned parameters, the system will appropriately limit the engine stopping and starting cycles to ensure that the battery recharges correctly.
Conclusion: The IBS exits the calibration stage when the SOC and SOF evaluations are within the tolerances, as shown in the previous table. This occurs after a rest stage (engine off) of at least 4 hours followed by a starting.
Use of information supplied by the IBS
In engine on conditions, the BCM uses the information received from the IBS to activate or deactivate a possible automatic stop on the basis of the battery starting capacity estimated by the IBS.
As already mentioned, the starting capacity of the battery is usually evaluated through the battery status, expressed as SOC, SOF, SOH and temperature; when, on the other hand, the IBS is being recalibrated, some status variables are not reliable and therefore only the SOF and the battery temperature are taken into account.
The request to enable/disable an automatic stop by the BCM is translated into a signal produced by the BCM and sent, through the Controller Area Network (CAN) C, to the ECM.
The following flow-chart describes the strategy used by the BCM to manage the information from the IBS and the automatic stop enabling/disabling.
When the engine automatic stop is enabled by the BCM, the ECM is enabled to automatically switch off the engine if the driving conditions (actions on the brake, clutch and accelerator pedals) are satisfied in the same way as the other conditions controlled by the ECM.
When the engine automatic stop is disabled by the BCM, the ECM is not enabled to automatically switch off the engine, even if the driving conditions (actions on the brake, clutch and accelerator pedals) are satisfied in the same way as the other conditions controlled by the ECM.
Engine automatically switched off conditions
When the engine has been automatically switched off for the Stop/Start function, a request can be generated by a device/control unit, which requires the automatic restarting of the engine.
The BCM collects the information coming from the vehicle and, if necessary, requires the ECM to automatically restart the engine (the ECM checks first whether safe automatic restarting conditions are satisfied).
The decision to request or not request an automatic stop by the BCM is translated into a signal produced by the BCM and sent, through the CAN-C, to the ECM.
The following flowchart describes the strategy used by the BCM to manage the information from the IBS and the procedure for asking/not asking for an automatic stop.
Cranking
Key startup is controlled by the user by placing the key in the starting position: under these circumstances starting is managed by BCM, and by ECM.
Inside the BCM is a relay, R2, the power line of which is in series with the power line of relay R1 managed by the ECM.
When the engine is started, both relays are closed. At the end of starting, the engine management module opens relay R2 and immediately afterwards orders brief closure of the same relay to diagnose the BCM relay: if the voltage level downstream of the relay is low, relay R1 has not become stuck. If instead the level is high, relay R1 has become stuck. A fault code will be set and the stop/start is disabled.
Starting by stop/start occurs according to the same logic as key starting, with the sole difference that the starting signal (+50) arrives at the BCM from the CAN and not from the switch.
In normal conditions, both relays are controlled only when the engine is started, both by key and by Stop/Start.
Failed engine cut out conditions - Conditions managed by the ECM
When the Stop/Start is activated, under certain circumstances the engine does not stop automatically due to comfort, emission control and safety reasons. These conditions leading to a failed automatic engine stop can be detected and managed by the BCM or by the ECM.
Engine cold: the automatic engine stop is not allowed if the signal from the engine coolant temperature sensor is outside of a range from about 40°C (104°F) and about 100°C (212°F). In this case the consumption and emission reduction derived from the Stop/Start is not guaranteed.
Reverse engaged: if reverse gear is engaged, the Powertrain Control Module does not allow the automatic stopping of the engine. In this way the driveability during parking is not compromised.
Clutch switch operation check not performed yet: This check takes place following a complete clutch pedal cycle (release and pressing or pressing and release) with the engine on
Malfunction or fault detected in at least one of the following sensors or systems:
- Accelerator pedal.
- Brake pedal.
- Vacuum sensor on brake servo.
- Transmission Control Module (TCM).
- Water temperature sensor in the engine.
- Wheel speed sensors.
- Clutch switch.
- Engine rpm sensor.
- Camshaft sensor.
- Reverse switch.
- Engine or Powertrain Control Module (PCM) (with MIL on).
- Braking system low vacuum: the ECM prevents the automatic engine stop if the vacuum sensor (see paragraph on the sensors detected by the ECM for details on the sensors) transmits a LOW value.
- The BCM asked to prevent the engine automatic stopping by sending a CAN-C message if one or more conditions managed by the BCM occur.
- For Diesel engines only: Particulate filter regeneration in progress; the PCM does not allow the automatic engine stop if the Diesel Particulate Filter (DPF) is carrying out the regeneration of the filter.
Conditions managed by the BCM - Battery not sufficiently charged or flat:
The BCM receives information from the IBS on the status of the battery charge. If the IBS is being recalibrated, the engine stop is not allowed if one of the following conditions occurs:
- the battery Function Status (SOF) is below 8.3 V
- the battery temperature is below -23°C (-9.4F)
If the IBS is not being recalibrated, the engine stop is not allowed if one of the following conditions occurs:
- the battery Charge Status (SOC) is below 75%
- the battery Health Status (SOH) is below 60%
- the battery Function Status (SOF) is below 8.2 V
- the battery temperature is below -23°C (-9.4F)
IBS failure: the automatic engine stop is not allowed if an IBS malfunction occurs.
Voltage Stabilizer failure: the automatic engine stop is not allowed if Voltage Stabilizer malfunction occurs.
Driver door not closed: the automatic engine stop is not allowed if the driver door is open
Driver seat belt unfastened: the engine automatic stop is not allowed if the driver seat belt is unfastened.
Outside temperature sensor:
when the vehicle is equipped with an outside temperature sensor, the automatic engine stop is not allowed if:
- the outside temperature is lower than the limit -14°C (6.8°F)
- the outside temperature is higher than the limit 80°C (176°F)
The temperature limits that have been set on the outside temperature sensor are "extreme" and therefore must always be respected.
Automatic climate control: the automatic engine stop is not allowed if the difference between the climate control temperature set by the customer and the temperature inside the passenger compartment is greater than ± 4°C (7.2°F). In the case of manual air conditioning, the engine can always be stopped.
Generator fault: the automatic engine stop is not allowed in the case of generator malfunction.
Engine hood open: if the vehicle is equipped with a hood switch, the automatic engine stop is not allowed if the hood is open.
Logistic Mode status active: the automatic engine stop is not allowed if the Logistic Mode status is active.
SPM semi-automatic parking system: when the vehicle is equipped with the semi-automatic parking system, the automatic engine stop is not allowed if the system is active.
Failure on BCM relay: the automatic engine stop is not allowed in the case of malfunction of the startup circuit relay operated by the BCM.
Automatic restarting - When the Stop/Start is operational, under certain circumstances the engine may restart automatically without any intervention by the driver due to comfort, emission control and safety reasons. These conditions leading to the engine automatic restarting can be detected and managed by the BCM or by the ECM.
Conditions managed by the ECM
- Braking system low vacuum: an automatic engine restart is forced if the vacuum sensor (see paragraph on the sensors detected by the ECM for details on the individual sensors) transmits a LOW value. This prevents undesired movements of the car with the engine off on a gradient due to a possible brake servo failure.
- Moving vehicle: An automatic engine restart is forced if the car speed is higher than a certain threshold, about 5 km/h (3 mph). This condition avoids dangerous situations due to a failure of the engine brake on gradients.
- Engine cut-off by the Stop/Start system for a time longer than 160 seconds.
- Engaged reverse: if the driver engages reverse gear during an engine stop by the Stop/Start, the Powertrain Control Module automatically restarts the engine. In this way the driveability during parking maneuverers is not compromised.
- Cold engine: the ECM forces the automatic engine restart if the signal from the engine water temperature sensor is below the threshold, about 30°C (86°F). In this case the reduction in consumption and emissions derived from the Stop/Start is not guaranteed.
- The BCM requested the automatic engine restart without any action by the driver and transmitted this information to the ECM by means of a specific message on CAN-C.
- Catalytic converter temperature below a given threshold (temp_catalyst).
- The handbrake is applied while the car is moving (either forward or in reverse) with the engine stopped at a speed higher than the threshold, (about 3 km/h / 2 mph) This is a further safety measure to avoid dangerous situations due to a failure of the engine brake on gradients
- For Diesel engines only DPF regeneration in progress: the Powertrain Control Module automatically reactivates the engine if the DPF is carrying out the regeneration of the filter.
Conditions managed by the BCM
Battery not sufficiently charged or flat:
The BCM receives information from the IBS on the status of the battery charge. If the IBS is being recalibrated, the engine is automatically restarted without any driver intervention if one of the following conditions occurs:
- the battery Function Status (SOF) is below 7.6 V
- the battery temperature is below -24°C (11.2°F)
If the IBS is not being recalibrated, the engine is automatically restarted if one of the following conditions occurs:
- the battery Charge Status (SOC) is below 70%
- the battery Health Status (SOH) is below 59%
- the battery Function Status (SOF) is below 7.3 V
- the battery temperature is below -24°C (11.2°F)
IBS fault: The engine is automatically restarted without any action by driver if an IBS malfunctioning occurs
Outside temperature sensor:
If an outside temperature sensor is fitted, the engine is automatically restarted without any action by driver if:
- the outside temperature is lower than the limit -14°C (6.8°F).
- the outside temperature is higher than the limit 80°C (176°F).
The temperature limits that have been set on the outside temperature sensor are "extreme" and therefore must always be respected.
Automatic climate control:
The engine is automatically restarted without any action by the driver if the difference between the climate control temperature set by the customer and the temperature in the passenger compartment is greater than ± 7°C (12.6°F).
In the case of manual air conditioning, the engine remains off.
Logistic Mode status active: The engine is automatically restarted without any action by the driver if the Logistic Mode status is activated.
Semi-automatic parking system SPM : When the vehicle is equipped with the semi-automatic parking system, the engine is automatically restarted without any action by the driver if the parking system is activated during the engine stopping stage.
Disabling of automatic restarting (safety function) - In some cases, after an automatic engine stop through the Stop/Start, it is possible that the automatic restart requested by the driver is not carried out. In these circumstances, restarting is only possible through manual intervention by the driver on the key, to restore the behavior of the vehicle to that of a traditional vehicle without S/S. The management of this function is transferred to the ECM and the BCM.
Conditions managed by the ECM
Too many unsuccessful attempts at automatic starting - The threshold Max_cranking_attempts (5 times) has been exceeded. The threshold indicates the maximum number of failed automatic engine restart attempts. This threshold is set to prevent damage to the starter by too many startup attempts close together.
The BCM requested to prevent the engine automatic restart. Malfunction or fault detected in at least one of the following sensors or systems:
- Accelerator pedal
- Brake pedal
- Brake servo vacuum sensor
- Engine coolant temperature sensor
- Vehicle speed
- Transmission Control Module (TCM)
- Clutch switch
- Neutral sensor
- Engine rpm sensor
- Camshaft sensor
- Reverse switch
- Engine or Powertrain Control Module (with MIL on).
The driver has been requested to perform an action but did not perform it in time - Engine at standstill timeout set by the threshold 175 seconds. If an automatic engine restart attempt is unsuccessful as a result of a failure to press the clutch or because the transmission is not in neutral and the driver is then requested to allow automatic restart by pressing the clutch or engaging neutral, the engine can only be restarted using the key after 175 seconds has elapsed from the engine restart attempt.
Conditions managed by the BCM
- Engine hood open: when the hood switch is fitted, automatic engine restarting is not allowed if the hood is open.
- Driver or passenger door not closed and driver seat belt unfastened: automatic engine restarting is not allowed if the driver door or the passenger door is open and, at the same time, the driver seat belt is not fastened.
- Failure on BCM relay: automatic engine restarting is not allowed in the case of malfunction of relay T20 controlled by the BCM.