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Central locking (CL (ZV)), function - GF80.20-P-0005FL

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MODEL 212 

Fig 1: Central Locking Function Diagram - Model 212
G10050475Courtesy of MERCEDES-BENZ USA

Central locking (CL [ZV]), general 

The CL controls electric locking and unlocking of the vehicle doors, the trunk lid (model 212.0/1), the liftgate (model 212.2.) and the fuel filler flap.

The following control elements are available:

IMPORTANT On model 212.2 with code (889) KEYLESS-GO, model 212.0/1 with code (881) Remote trunk closing and code (889) KEYLESS-GO):

The trunk lid or liftgate can be closed and the central locking locked using the following control points:

For this purpose detailed information is given in the separate partial function KEYLESS-GO.

The CL comprises the following partial functions:

Additional function requirements for operation with transmitter key 

Function sequence for control with transmitter key 

The central locking can be operated with the transmitter key. The transmitter key operation comprises the following partial functions:

Function sequence for presetting global and selective unlocking 

If the unlock and lock buttons on the transmitter key are pressed simultaneously for t = 5 s, a change between the "global" and "selective" settings takes place. The indicator lamp on the transmitter key comes on for confirmation.

Globally unlocking:

The entire vehicle is unlocked by pressing the "Unlock" button on the transmitter key.

Selective unlocking:

Only the driver door and the fuel filler flap are unlocked when the "Unlock" button on the transmitter key is pressed once. The next actuation unlocks the entire vehicle.

Function sequence for locking or unlocking 

Vehicles without code (889) KEYLESS-GO:

When the unlock button or lock button on the transmitter key is actuated, it transmits a radio signal (access authorization) to the rear SAM control unit via the rear window antenna and FM 1, AM, ZV and KEYLESS-GO antenna amplifier. This relays the signal to the electronic ignition lock control unit via interior CAN.

Vehicles with code (889) KEYLESS-GO:

When the unlock button or lock button on the transmitter key is actuated, it transmits a radio signal (drive authorization) to the KEYLESS-GO control unit via the rear window antenna and FM 1, AM, CL and KEYLESS-GO antenna amplifier.

The KEYLESS-GO control unit sends the radio signal (access authorization) to the electronic ignition lock control unit via interior CAN.

Parallel to the radio signal (access authorization), an infrared signal is transmitted to the driver front door infrared remote control receiver (precise aiming required). This signal is read in by the left front door control unit and transmitted to the electronic ignition lock control unit via interior CAN.

IMPORTANT The infrared and radio signals include the same information (redundant); the first signal received is accepted. This function serves for operating safety in the event that e.g. the radio signal is blocked by interference such as electromagnetic fields.

In both cases the electronic ignition lock control unit checks the access authorization of the transmitter key. If the access authorization is valid, the electronic ignition lock control unit transmits the request "Lock" or "Unlock" via the interior CAN to the following control units:

The left front door control unit locks or unlocks the left front door lock via the left front door central locking motor. The right front door control unit locks or unlocks the right front door lock via the right front door central locking motor. The left rear door control unit locks or unlocks the left rear door lock via the left rear door central locking motor. The right rear door control unit locks or unlocks the right rear door lock via the right rear door central locking motor.

The rear SAM control unit locks or unlocks the tank cap via the tank cap central locking motor.

The rear SAM control unit inhibits the opening request via the trunk lid external operation switch (model 212.0/1) or liftgate external operation switch (model 212.2) or enables the request accordingly.

The status of the vehicle doors as well as the trunk lid or liftgate is sensed over the following switches:

The corresponding door, trunk lid or liftgate is locked or unlocked, depending on the status (open or closed).

On vehicles with code (885) Extended theft protection, the following components are actuated additionally:

IMPORTANT Vehicles with code (551) Anti-theft alarm system (ATA [EDW]):

If the driver door in the locked vehicle is opened mechanically with the emergency key, the anti-theft alarm system (ATA) triggers an alarm.

Function sequence for acoustic locking feedback (as of 1.6.10) 

The acoustic locking feedback function is selected via the control level in the instrument cluster.

The instrument cluster transmits the corresponding status via interior CAN to the front SAM control unit.

When the function is activated, the front SAM control unit momentarily actuates the left horn and the right horn via the horn relay after successful locking and unlocking. For this purpose the electronic ignition lock control unit transmits the "Lock" or "Unlock" request to the front SAM control unit via the interior CAN.

Number of acoustic signals:

If, during locking a door, the trunk lid (model 212.0/1) or the liftgate (model 212.2) is open, the acoustic locking feedback does not sound. The front door control units transmit the status of the corresponding front door to the electronic ignition lock control unit via the interior CAN. The rear SAM control unit sends the circuit status of the corresponding rear door to the electronic ignition lock control unit via the interior CAN.

Function sequence for optical locking feedback 

After the CL is locked or unlocked successfully, a visual feedback is output via the turn signals.

The electronic ignition lock control unit transmits the request "Lock" or "Unlock" to the front SAM control unit via the interior CAN. The front SAM control unit then actuates the hazard warning flashing function by means of outputting the flasher frequency over the interior CAN. All turn signals are actuated synchronously on the vehicle.

One flashing cycle is output when unlocking.

Three flashing cycles are output when locking.

If a door is still open when locking, there is no visual feedback.

The front door control units transmit the status of the corresponding front door to the electronic ignition lock control unit via the interior CAN. The status of corresponding rear doors is sent by the rear SAM control unit over the interior CAN.

IMPORTANT Detailed information on performing the hazard warning flasher function is included in the function description "Exterior lights, function" in the sub-function "Turn signal light actuation, function".

Function sequence for remote trunk opening (model 212.0/1), trunk lid control (model 212.0/1 with code (881) Remote trunk closing (RTC)) or liftgate control (model 212.2) 

Vehicles without code (889) KEYLESS-GO:

When the trunk lid/liftgate remote opening button on the transmitter key is actuated, it transmits a radio signal (access authorization) to the rear SAM control unit via the rear window antenna and FM 1, AM, CL and KEYLESS-GO antenna amplifier. This relays the radio signal (access authorization) to the electronic ignition lock control unit via interior CAN.

Vehicles with code (889) KEYLESS-GO:

When the trunk lid/liftgate remote opening button on the transmitter key is actuated, it transmits a radio signal (access authorization) to the KEYLESS-GO control unit via the rear window antenna and FM 1, AM, CL and KEYLESS-GO antenna amplifier.

The KEYLESS-GO control unit sends the radio signal (access authorization) to the electronic ignition lock control unit via interior CAN.

The electronic ignition lock control unit checks the transmitter key's access authorization. If the access authorization is valid, the electronic ignition lock control unit transmits the request "Unlock" to the rear SAM control unit via the interior CAN.

On model 212.0/1 without code (881) Remote trunk closing (RTC), the rotary tumbler of the trunk lid is unlocked via the trunk lid central locking motor. The trunk lid is then opened mechanically by spring force as far as the upper stop.

On model 212.0/1 with code (881) Remote trunk closing (RTC) or model 212.2, the rotary tumbler of the trunk lid or liftgate is unlocked via the trunk lid central locking motor or liftgate central locking motor. Then the trunk lid or liftgate is opened automatically.

IMPORTANT Model 212.0/1 with code (881) Remote trunk closing (RTC):

Detailed information on trunk lid control is given in the function description "Trunk lid control".

Model 212.2: Detailed information on liftgate control is given in the function description "Liftgate control".

Additional function requirement for vehicles with locking/unlocking inside switch 

Function sequence for locking/unlocking vehicle with inside switch 

The central locking (CL) can be operated with the left front door central locking inside door handle switch and right front door central locking inside door handle switch.

The vehicle function locking/unlocking with interior switch comprises the following partial functions:

Function sequence for locking/unlocking CL 

When the left front door central locking inside door handle switch or right front door central locking inside door handle switch is pressed, the vehicle doors are unlocked or locked. The left front door control unit reads in the status of the left front door central locking inside door handle switch. The right front door control unit reads in the status of the right front door central locking inside door handle switch. Then the corresponding front door control unit transmits the status of the front door central locking inside door handle switch via the interior CAN to the electronic ignition lock control unit.

The electronic ignition lock control unit then transmits the request "Unlock" or "Lock" via the interior CAN to the following control units:

The left front door control unit locks or unlocks the left front door lock via the left front door central locking motor. The right front door control unit locks or unlocks the right front door lock via the right front door central locking motor.

The left rear door control unit locks or unlocks the left rear door lock via the left rear door central locking motor. The right rear door control unit locks or unlocks the right rear door lock via the right rear door central locking motor.

The rear SAM control unit inhibits the opening request via the trunk lid external operation switch (model 212.0/1) or liftgate external operation switch (model 212.2) or enables the request accordingly.

When locking via the central locking inside door handle switch the tank cap remains unlocked.

The locking functions are enabled depending on the door status.

Opening a door from the inside when the CL is locked:

Basically each door can be opened from the inside (except with code (885) Extended theft protection with active additional door lock or when the mechanical child safety lock on the rear doors (without code (494) USA version) is activated). The corresponding door can be opened manually.

If the vehicle was unlocked globally before locking, the CL is actuated centrally.

Additional function requirement for unlocking trunk lid or liftgate (opening) 

IMPORTANT The instrument cluster transmits the speed information to the rear SAM control unit via the interior CAN.

The unlocking trunk lid or liftgate (opening) function comprises the following subfunctions:

Function sequence for opening via trunk lid release button (model 212.0/1 without code (881) Remote trunk closing (RTC)) 

Actuation of the trunk lid release button for t ≥0.5 s is read in directly by the left front door control unit and relayed to the rear SAM control unit via interior CAN. This unlocks the rotary tumbler on the trunk lid via trunk lid central locking motor. The trunk lid is opened up to the upper stop by spring force.

Function sequence for opening via driver trunk lid/liftgate control button (model 212.0/1 with code (881) Remote trunk closing (RTC), model 212.2) 

Actuation of the driver trunk lid/liftgate control button for t ≥0.5 s is read in directly by the left front door control unit and relayed to the rear SAM control unit via the interior CAN. This unlocks the rotary tumbler of the trunk lid or liftgate via the trunk lid central locking motor or liftgate central locking motor. Then the trunk lid or liftgate is opened automatically.

IMPORTANT Model 212.0/1: Detailed information on trunk lid control is given in the function description "Trunk lid control".

Model 212.2: Detailed information on liftgate control are given in the function description "Rear door remote actuation, function".

Function sequence for opening via trunk lid emergency opening switch (model 212.0/1 with code (494) USA version) 

This function is always activated (regardless of the CL status), because it allows the trunk lid to be opened by a person trapped in the trunk. The trunk lid emergency opening switch is located on the inside of the trunk lid and is read in by the rear SAM control unit. When the trunk lid emergency opening switch is actuated, the rear SAM control unit actuates the trunk lid central locking motor to unlock the rotary tumbler. The trunk lid is opened up to the upper stop by spring force.

Additional function requirements for automatic locking 

IMPORTANT To activate automatic locking, activate one of the central locking closing switches (S85/5s2 or S85/6s2) for t > 5 s. To deactivate actuate one of the central locking opening switches (S85/5s1 or S85/6s1) for t > 5 s. Actuation or deactivation of this function is indicated to the driver by an acknowledgment sound in the instrument cluster.

Function sequence for automatic locking 

The vehicle is automatically locked under certain conditions.

The automatic locking function comprises the following partial functions:

Function sequence for locking, depending on vehicle speed 

When the vehicle exceeds the limit value for the vehicle speed of v = 3 km/h, the rear SAM control unit prevents the trunk lid (model 212.0/1) of liftgate (model 212.2.) from being opened from the outside.

The rear SAM control unit reads in the status of the trunk lid external operation switch (model 212.0/1.) or liftgate external operation switch (model 212.2.) and ignores the opening request. When the vehicle moves faster than v = 15 km/h, the doors are locked automatically. The instrument cluster transmits the vehicle speed via the interior CAN to the electronic ignition lock control unit.

The electronic ignition lock control unit evaluates all relevant information and sends the "locking" request to the following control units via the interior CAN:

The left front door control unit locks the left front door lock via the left front door central locking motor. The right front door control unit locks the right front door lock via the right front door central locking motor. The left rear door control unit locks the left rear door lock via the left rear door central locking motor. The right rear door control unit locks the right rear door lock via the right rear door central locking motor. Under the following conditions, the automatic CL locking function is canceled, i.e. the CL is unlocked:

IMPORTANT When the vehicle is unlocked by actuating the central locking inside door handle switch, it remains unlocked even above the limit for the vehicle speed.

It is not possible to open the trunk lid or liftgate from the outside even when the vehicle is standing still when it has been locked automatically previously by the CL. If a door is opened while driving and then closed again, and the vehicle speed is above the limit for automatic locking, the door is locked again after it is closed.

Additional function requirement for automatic relocking 

Function sequence for automatic relocking 

After the vehicle is unlocked with the transmitter key, a waiting time of t = 40 s starts. After expiration of this waiting time, the vehicle is locked again, if a door, the trunk lid or liftgate was not opened previously.

Visual feedback is not performed.

IMPORTANT The anti-theft alarm system (ATA) (on vehicles with code (551) Anti-theft alarm system (ATA)) is also activated by the automatic relocking function.

With code (885) Extended theft protection, an additional door lock is activated.

Additional function requirement for emergency opening in event of crash 

Function sequence for emergency opening in event of crash 

The emergency opening function unlocks the doors of the vehicle after an accident. The supplemental restraint system control unit sends the crash signal to the electronic ignition lock control unit and front SAM control unit via chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13). The front SAM control unit transmits the crash signal via the interior CAN to the following control units:

After a waiting time of t = 8 to 11 s, the doors are unlocked.

The emergency opening function overrides all other central locking functions. When the vehicle has been locked from the outside, the emergency opening function is not active.

Function sequence for mechanical locking of trunk lid (model 212.0/1 without code (887) Valet Parking) 

The mechanical trunk lid locking feature allows valuables to be locked in the trunk intentionally. Mechanical locking of the trunk lid is defined via the status of the trunk lid contact switch. The trunk lid contact switch can be actuated by turning the emergency key of the trunk lid lock cylinder. The rear SAM control unit directly reads in the status of the trunk lid contact switch and inhibits opening requests from other control points.

Additional function requirements for additional door lock (with code (885) Extended theft protection) 

Function sequence for additional door lock (with code (885) Extended theft protection) 

The mechanical inside door handle is decoupled mechanically by the additional door lock when the central locking is locked. It is no longer possible to open the doors from the inside. This prevents breaking in into the vehicle by smashing in a window and opening a door from inside.

Upon locking with the central locking, the electronic ignition lock control unit also sends the request "Additional locking" to the following control units, via the interior CAN:

The left front door control unit actuates the left front door additional door lock actuator motor in the left front door lock. The right front door control unit actuates the right front door additional door lock actuator motor in the right front door lock. The left rear door control unit actuates the left rear door additional door lock actuator motor in the left rear door lock. The right rear door control unit actuates the right rear door additional door lock actuator motor in the right rear door.

Function sequence for play protection 

Each actuation of the CL [ZV] is counted by the electronic ignition lock control unit. Every t = 7 s one actuation is deducted from the current counter status. The maximum number of actuations is 40. If this value is reached, additional actuation requests are not accomplished for the CL [ZV]. Actuation of the CL [ZV] again is possible only after dropping below this value again.

  Electrical function diagram for central locking (CL [ZV]) MODEL 212.0/1 PE80.20-P-2050-97DAA 
MODEL 212.2 PE80.20-P-2050-97DAB 
  Overview of system components for theft protection and locking   GF80.00-P-9999FL 
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