All about the functions of the Coming Home and Leaving Home
A modern car is a concentration of advanced engineering in the form of many different systems, which make driving the car easier and more comfortable for the driver and passengers. The Germans, in particular the engineers of Volkswagen automobile concern, have especially succeeded in it. Cars of this brand can be called a testing ground for the newest systems which at first were absent at the competitors. As an example we can mention the Coming Home/Leaving Home function, which after successful testing appeared on the cars of Skoda, Audi and even Bugatti.
What are the Coming Home/Leaving Home options
How much money will be paid for these functions, if they are not included into the purchased equipment? The question is far from being idle, especially for those who are not familiar with these functions and have no idea what they are for.
Generally speaking, we can say that the Coming Home/Leaving Home functions are components of the Light Assistant system, the purpose of which is to increase driver comfort in low-light conditions.
Both functions provide some extra operating time for the headlights when the car is put on protection, as well as when it is taken off protection. Which function is responsible for what, you can guess from the name: Coming Home translates as “coming home”. If it is on, then after activation of the car protection function by means of a key fob, the dipped headlights will be on immediately, which will help the driver to get home or go out on a lighted road without any problems. After a set period of time the headlights will go out.
Leaving Home acts exactly the opposite, turning on the headlights immediately after removing protection, which allows you to get to the place of parking the car without turning on the exterior lights at home (because it would still have to turn off, if you do not have a system of “smart home”).
Note that the implementation of these functions can be variable. So, on some models of cars that have this functionality, instead of dipped headlights use fog lights.
How the Coming Home/Leaving Home functions work
There are a number of conditions that must be met for these functions to work properly:
- This function must be present in the “brains” of the on-board computer;
- The function must be activated;
- Switching on/off the Coming/Leaving Home function is done by the ECU;
- The on-board computer must know that it is dark outside, using the information transmitted by the light sensor.
The implementation of the algorithm, as noted above, can vary depending on the make/model. There are implementations where the additional short-term light turns on automatically without requiring any action from the car owner. Some models require you to “blink” the headlights a few times before leaving the car to activate Coming Home.
Advantages and disadvantages of Coming/Leaving Home
We can not say definitively whether this feature is useful or useless, because its use may be required often or periodically even for one and the same car owner. So each driver must decide for himself how necessary this option can be and whether it is worth overpaying for it.
Let’s note the obvious advantages of both functions:
- if you have to leave your car in the dark on unlit areas (it can be a parking lot, a place near an apartment building or a private house), it will help to get to the car or get away from it. Most often this functionality is relevant for the inhabitants of the suburbs, especially if there is no street lighting near the house;
- the same can be said about finding a car in large unlit parking lots, especially if you do not remember exactly where you left your car.
There’s only one disadvantage to the features: they use battery power, reducing its charge. If your battery is not in the best condition, even a brief inclusion of dipped headlights can lead to its discharge, and in the morning you will have to find ways to bring the power unit into working order. To be fair, it should be noted that this scenario is unlikely, because the dying auto battery in any case will make itself known much earlier, and you can disable this feature in advance.
Road lighting system for home/road from home Mazda cars
The “coming home light / leaving home light” function of Mazda vehicles
The “coming home light / leaving home light” function can be used to help maintain visibility in front of the vehicle by turning on the passing headlight / dipped headlight, front and rear clearance lamps, license plate lamps when the car is parked at night.
Mazda “coming home light” system
By briefly pushing the steering column switch to the high beam (FLASH-TO-PASS) position when the ignition is off or the ignition is in the accessory position (ACC), the coming home light system turns on the low beam (LO) headlights for a specified time after a person leaves the vehicle.
The road home lighting system controls the low beam headlights using the following two functions:
Standby function, which turns on the dipped lights when the lever is briefly moved to the FLASH-TO-PASS position and lasts until the user exits the vehicle.
A light-off timer function that activates when the user exits the vehicle and closes all doors when the system wait function is activated.
A system wait function for the road home light system:
When the body control module (BCM) receives a signal to move the lever to the FLASH-TO-PASS position with the ignition off or the ignition in the ACC position, it turns on the dipped headlight (LO). After 3 minutes from when the system goes into standby, or when another FLASH-TO-PASS signal is received during standby, the body control module (BCM) turns the headlights off.
The function of the timer to turn off the lights of the road home lighting system:
The body control module (BCM) on standby turns the light off timer on when all door limit switch signals are received (doors closed) after receiving an open door signal (user has exited the vehicle). If this detects an open door position limit switch signal, the system returns to standby mode. When the light switch-off timer expires, the Body Control Unit (BCM) turns off the headlights(LO).
The light off timer setting can be changed to 120 seconds (initial setting is [30 seconds]).
System operation procedure in standby mode:
– The ignition is off or in the ACC position – The light off timer (personalization setting) is not set to [Off] – No automatic light off timer countdown in the VSM module
1. When the steering column switch lever is moved to the FLASH-TO-PASS position, the instrument cluster receives a (1) FLASH-TO-PASS signal.
2. The instrument cluster sends the (2) FLASH-TO-PASS signal to the body control module (BCM) through the CAN bus.
3. When the Body Control Module (BCM) receives FLASH-TO-PASS under operating conditions, it turns on the dipped headlight (3) and the system goes into standby mode.
Order of operation in light-off timer mode:
– All closed door limit switch signals are received by the BCM module (doors closed) after the module detects any open door position (door open) limit switch signal.
1. When the Body Control Module (BCM) detects all door limit switch signals in the closed position (1) after receiving any door open standby signal, it turns on (2) the light off timer.
2. When the timer expires, the Body Control Module (BCM) sends a dipped light OFF signal to the Headlight Control Module.
3. When the light control module receives the off signal from the BCM, it turns off the dipped beam (LO) (4).
Mazda “leaving home light” road lighting system
When the car door lock is opened with the remote transmitter with the ignition off and the light stalk switch in the HEAD, AUTO or TNS (parking lights) position, the leaving home light system turns on the low beam (LO) and TNS headlights for a preset time.
The function of the timer to turn off the road lighting system from the house:
When the BCM receives a door lock request signal from a remote transmitter with the light switch in the TNS (parking lights), AUTO or HEAD position and the ignition off, it turns on the dipped beam headlights, TNS and controls the system light off timer. The Body Control Module (BCM) turns off the headlights and TNS (parking lights) when the light-off timer expires (30 sec). If the BCM receives a door lock request signal from a remote transmitter while the light off timer is operating, it turns off the headlights (LO) and TNS. * 1
* 1: If the light switch is in the TNS (parking lights) position, the parking lights are not switched off.
Personalization options: The home-road lighting system can be switched between the operating and non-operating states (initial setting is [On]).
How the road lighting system works from home:
– Light switch in TNS (parking lights), AUTO or HEAD position
– The door lock release request signal is received from the remote control transmitter
– The light’s timer does not count down automatic deactivation.
The light switch is in AUTO or HEAD position.
1. When the unlock button on the remote transmitter is pressed, the body control module (BCM) receives (1) the door lock release request signal.
2. The instrument cluster sends (2) light ON signal to the body control module (BCM) via CAN bus. 3.
The body control module (BCM) sends (2) door lock release request signal to the door power supply unit.
4. If the initial conditions have been met, the Body Control Module (BCM) turns on the TNS and the low beam headlights (LO) (3).
5. The body control module (BCM) turns off the TNS and the headlights (LO) when the light-off timer has expired (4).
The light switch is in the TNS (parking lights) position.
The procedure is the same as above except in step 5 where the body control module (BCM) only turns off the headlights (4) while leaving the TNS (parking lights) on.