Electrical seat adjustment (ESA) - GF91.29-P-0009RF

Model 205, 253 with code 275 (Memory package) except code 221 (Electrically adjustable left driver seat) except code 222 (Electrically adjustable right front seat) 

Function requirements, general 

• No overvoltage or undervoltage

Electrical seat adjustment (ESA), general 

The ESA enables the electrical adjustment of the driver and front passenger seat. The driver and front passenger seat can be adjusted as follows:

• Seat fore/aft position
• Backrest inclination
• Seat height
• Seat inclination
• Seat cushion length
• Head restraint height

Furthermore, the respective seat position can be stored and called up together with other settings.

Priorities:

The seat adjustment is divided up into three groups and three priorities. Each adjustment in a group is independent from an adjustment in another group. If adjustment requests for several adjustments are received in a group by the driver seat control unit or the front passenger seat control unit, the adjustment request with the highest priority is carried out.

The priorities are determined as follows:

Group 1:

• High priority: seat fore/aft adjustment, steering column fore/aft adjustment (driver seat only)
• Low priority: seat inclination adjustment

Group 2:

• High priority: backrest inclination, steering column adjustment up/down (driver's seat only)
• Low priority: seat height adjustment

Group 3:

• High priority: head restraint adjustment, seat cushion length

The ESA includes the following subfunctions:

• Function sequence for position detection 
• Function sequence for normalization 
• Function sequence for antilock device 
• Function sequence for manual adjustment 
• Function sequence for saving and retrieving seat positions 
• Function sequence for head restraint presetting 
• Function sequence for front passenger head restraint lowering mechanism (with CODE 242 (Electrically adjustable front passenger seat with memory function)) 
• Function sequence for collision avoidance with rear bench seat (model 205.0/1 with CODE 287 (Folding rear seat backrests), model 205.2, 253) 
• Function sequence for PRE-SAFE® front passenger seat positioning function (with CODE 242 (Electrically adjustable front passenger seat with memory function) and CODE 299 (PRE-SAFE® system)) 
• Fault handling function sequence 

Function sequence for position detection 

The seat adjustment motors are equipped with Hall sensors. The signals from the Hall sensors are read in and evaluated by the driver's seat control unit or the front passenger seat control unit directly.

Normalization resets a location counter in the driver's seat control unit or the front passenger seat control unit. During seat adjustments, the driver seat control unit or the front passenger seat control unit defines the adjustment range of the seats by counting the Hall sensor signals.

Additional function requirements for normalization 

• Circuit 15R ON

The electronic ignition lock control unit sends the status of circuit 15 over the interior CAN to the driver seat control unit and to the front passenger seat control unit.

Function sequence for normalization 

Normalization is the basis for assigning the instantaneous position to the seat position that is recorded by the driver seat control unit or the front passenger seat control unit. Normalization must be performed during initial startup or in a denormalized condition.

The following mechanical stops have to be moved to for the normalization procedure:

• Front end stop for seat fore/aft position and backrest inclination
• Downstop of seat height and head restraint height
• Upper stop of seat inclination
• Rear end stop of seat cushion length

To this end, the corresponding switch in the seat adjustment switch group must remain actuated for t = 250 ms after the mechanical end stop has been reached. Upon successful normalization, the driver seat control unit or the front passenger seat control unit switches off the corresponding seat adjustment motor. During the initial startup, the normalization is performed with the diagnostic tester.

An adjustment is denormalized if the signal of the corresponding Hall sensor is not received. The denormalization procedure can also be performed via diagnosis.

Function sequence for antilock device 

If the Hall sensor signals are not received for an active adjustment for t > 2 s, this is recognized as blocking and the corresponding adjustment function is deactivated after t = 2 s by the driver seat control unit or the front passenger seat control unit. Reactivation in the same adjusting direction is not possible until the corresponding switch has been released for approx. t ≥ 2 s. Re-enabling in the opposite adjustment direction is immediately possible.

Function sequence for manual adjustment 

The manual setting is made with each front switch group, seat adjustment. Operation of the front switch group, seat adjustment is read in over each front door LIN by the respective front door control unit. The respective front door control unit sends the adjustment requests via interior CAN to the driver seat control unit or to the front passenger seat control unit. To adjust, hold down the switches in the front switch group, seat adjustment until the desired position is reached.

The driver seat control unit or the front passenger seat control unit actuates the following seat adjustment motors directly depending on the request:

• Seat adjustment motor, seat fore/aft adjustment
• Seat adjustment motor, head restraint adjustment'
• Seat adjustment motor, backrest inclination
• Seat adjustment motor for seat cushion length adjustment
• Seat adjustment motor for seat inclination adjustment
• Seat adjustment motor for seat height adjustment

Additional function requirements for saving and retrieving seat positions 

• ESA normalized

Function sequence for saving and retrieving seat positions 

There are two button operation options for storing the seat position:

• Press and hold left front or right front memory function switch, then press corresponding memory switch 1, 2 or 3 for relevant memory.
• Press and release left front or right front memory function switch for t > 100 ms, then press corresponding memory switch 1, 2 or 3 within 0.2 s ≤ t ≤ 3 s for the relevant memory.

The respective front door control unit reads in the status of the switches in the front switch group, seat adjustment via front door LIN and sends the request "Store memory position" via interior CAN to the driver seat control unit or the front passenger seat control unit. The driver's seat control unit or front passenger seat control unit uses the signals of the Hall sensors to store the current seat position.

Successful storage of the seat position is confirmed by the instrument cluster speaker with an acknowledgment tone. The request for this is sent by the driver seat control unit or the front passenger seat control unit over the interior CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster, which actuates the instrument cluster speaker directly.

To retrieve saved positions, press and hold corresponding memory switch 1, 2 or 3 until the stored end position is reached. Releasing leads to immediate termination of the adjustment procedure.

The respective front door control unit reads in the status of the switches in the front switch group, seat adjustment via front door LIN and sends the request "Adopt memory position" via interior CAN to the driver seat control unit or the front passenger seat control unit. The driver seat control unit or the front passenger seat control unit actuates the corresponding seat adjustment motors directly.

Abort conditions:

• Manual seat adjustment
• Manual mirror adjustment (driver only)
• Manual steering column adjustment (driver only)
• Pressing other memory switches

Compensating movements:

If collisions occur despite the defined priorities, compensating movements are started. When adjusting the backrest toward the rear, the seat fore/aft adjustment, seat height adjustment and seat inclination adjustment are ended first and the backrest is then positioned.

When adjusting the seat fore/aft adjustment to the rear, the seat backrest adjustment to the rear and the seat height adjustment upwards, the memory setting is implemented according to the following procedure:

• Seat fore/aft adjustment to the rear up to the characteristic map limit, then seat inclination adjustment
• Stop seat fore/aft adjustment at characteristic map limit
• Seat height adjustment until memory position is reached, then seat inclination adjustment
• Seat fore/aft adjustment until memory position is reached, then seat inclination adjustment
• Seat backrest adjustment until memory position is reached, then seat inclination adjustment

Additional function requirements for head restraint presetting 

• ESA normalized

Function sequence for head restraint presetting 

The height of the head restraint is automatically preset by the driver seat control unit or by the front passenger seat control unit depending on the seat fore/aft position. If the seat is moved forward, the head restraint moves down. If the seat is moved back, the head restraint moves up. The head restraint is adjusted in stages.

The head restraint presetting function can be switched on and off using a diagnostic tester and is coded after installation according to the country.

Additional function requirements for front passenger head restraint lowering mechanism (with CODE 242 (Electrically adjustable front passenger seat with memory function)) 

• Circuit 15R ON
• ESA normalized

The status of circuit 15 is sent by the electronic ignition lock control unit to the front passenger seat control unit via interior CAN.

Function sequence for front passenger head restraint lowering mechanism (with CODE 242 (Electrically adjustable front passenger seat with memory function)) 

If the front passenger seat is not occupied, the head restraint moves to the lower end stop in order to improve the rear passenger's view to the front. When the passenger side seat is occupied, the head restraint moves back to its original position. This function is executed by the front passenger seat control unit only.

The function is activated depending on the seat belt buckle status and the seat occupancy recognition on the front passenger seat. The supplemental restraint system control unit sends the status of the seat occupied recognition and the status of the belt buckle over the user interface CAN, electronic ignition lock control unit and interior CAN to the front passenger seat control unit. The front passenger seat control unit actuates the front passenger seat head restraint adjustment motor correspondingly.

Additional function requirements for collision avoidance with rear bench seat (model 205.0/1 with CODE 287 (Folding rear seat backrests), model 205.2, 253) 

• ESA normalized
• Vehicle speed v < 5 km/h
• Circuit 15 Off (driver seat only)

The instrument cluster sends the vehicle speed via user interface CAN, electronic ignition lock control unit and interior CAN to the driver seat control unit and to the front passenger seat control unit.

The electronic ignition lock control unit sends the status of circuit 15 over the interior CAN to the driver seat control unit and to the front passenger seat control unit.

Function sequence for collision avoidance with rear bench seat (model 205.0/1 with CODE 287 (Folding rear seat backrests), model 205.2, 253) 

The status of the backrest at the left/right rear (unlocked or locked) and the backrest inclination is recorded by the rear SAM control unit. To do so, the rear SAM control unit reads in the status of the rear backrest lock switch and the rear backrest inclination switch directly and then sends the status of the respective backrest via interior CAN to the driver seat control unit or to the front passenger seat control unit. The driver seat control unit or the front passenger seat control unit evaluates the current position of the front seats and checks whether a collision hazard exists with the corresponding front seat when folding down the respective backrest in the rear. If there is a collision hazard with the driver or front passenger seat when folding down the respective backrest, the driver seat control unit or front passenger seat control unit initiates the following measures:

• The driver or front passenger seat is moved forward if it is positioned too far to the rear (seat fore/aft adjustment)
• The driver and front passenger seat backrest are set upright if they are inclined too far (seat fore/aft adjustment)
• The driver or front passenger seat is moved up if it is positioned too far down (seat height adjustment)

On vehicles with CODE 494 (USA version), it is not possible to manually adjust the respective front seat to the collision zone if the rear backrest is unlocked. On vehicles except CODE 494 (USA version), it is possible to manually adjust to the collision zone during the collision avoidance function with the rear seat bench.

Abort conditions:

• Locking of backrest in rear
• Actuating left front switch group, seat adjustment

After interruption of the function, the driver or front passenger seat including on vehicles with CODE 494 (USA version), can be adjusted without limitation.

If the backrest in the rear is locked again, the corresponding front seat remains in its current position. They are not automatically moved to the initial position.

To trigger the collision avoidance with the rear bench seat function again, the system must detect that the rear backrest has been locked again.

With an unlocked backrest in the rear that is not folded forward, a message is issued by the instrument cluster. The rear SAM control unit sends the status of the respective backrest via interior CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster.

Additional function requirements for PRE-SAFE® front passenger seat positioning function (with CODE 242 (Electrically adjustable front passenger seat with memory function) and CODE 299 (PRE-SAFE® system)) 

• ESA normalized
• Front passenger seat occupied

The supplemental restraint system control unit sends the status of the seat occupied recognition via user interface CAN, electronic ignition lock control unit and interior CAN to the front passenger seat control unit.

Function sequence for PRE-SAFE® front passenger seat positioning function (with CODE 242 (Electrically adjustable front passenger seat with memory function) and CODE 299 (PRE-SAFE® system)) 

The front passenger seat PRE-SAFE® positioning function is activated at a critical driving condition, i.e. in a potential accident situation. This seat adjustment that takes place prior to the potential impact is supposed to achieve better occupant positioning for the subsequent accident.

The Electronic Stability Program control unit sends the request for adjusting PRE-SAFE® over the chassis FlexRay, electronic ignition lock control unit and interior CAN to the front passenger seat control unit.

Fault handling function sequence 

The driver seat control unit or the front passenger seat control unit checks the requests for seat settings it has received for plausibility. Adjustment requests for the same adjustment function in an opposite direction (e.g. backrest inclination forward//back simultaneously) are rejected. Correct requests for other adjustment functions remain unaffected. The plausibility of a manual adjustment request for a memory adjustment is checked by the left front door control unit or the right front door control unit.

	Electrical function schematic for seat adjustment (ESA)		PE91.29-P-2059-97FBA
	Overview of system components, electric seats		GF91.29-P-9992RF