GF91.29-P-0002RI Electric Seat Adjustment With Memory, Function
GF91.29-P-0002RI Electric Seat Adjustment With Memory, Function
- as of model year 2009 [models 230.4 except 230.479]
- with CODE (P99) Special model "AMG Black Series" [model 230.479]
- with CODE (494) USA version [model 230.479]
- as of model year 2009 except CODE (P99) [model 230.479]
Function requirements, general
^ No overvoltage or undervoltage
The EIS [EZS] control unit (N73) transmits the circuit status and the on-board electrical system voltage via interior CAN (CAN B).
Function description of electric seat adjustment (ESV [ESA]) with memory, general
The seat adjustment is described at the driver seat for left-hand drive vehicles as an example; the same is valid for the front passenger seat.
The following electric adjustments are possible:
- Seat fore/aft position
- Backrest angle
- Seat height
- Seat inclination
- Seat cushion length
- Head restraint height
Moreover, it is possible to store and move to the particular seat position.
On the driver-side, the positions of the outside mirrors and the steering column are also stored and retrieved via the memory function.
Priorities
The seat adjustment is divided up into 2 groups and 3 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 left front seat adjustment control unit with memory (N32/1), the adjustment request with the highest priority is performed.
The priorities are determined as follows:
Group 1
Priority high, height adjustment
Priority average, fore/aft adjustment
Priority low, seat cushion fore/aft adjustment
Group 2
Priority high, backrest adjustment
Priority average, inclination adjustment
Priority low, head restraint adjustment
If another adjustment is made in addition to the longitudinal adjustment, the head restraint presetting function is not executed.
Fault handling
The left front seat adjustment control unit with memory checks the requests received for seat adjustments for plausibility. Correct requests for other adjustment functions remain unaffected.
The electric seat adjustment enables the following subfunctions:
^ Manual adjustment
^ Saving and retrieving seat positions
^ Head restraint presetting
^ Synchronizing
^ Position measurement
^ Anti-lock device
^ Collision avoidance
^ Rear compartment access
Manual adjustment
The manual adjustment takes place via the left seat adjustment switch group (S91/2). The left seat adjustment switch group is read in directly by the left door control unit (N69/1).
The left door control unit transmits the requests from the left seat adjustment switch group to the left front seat adjustment control unit with memory via interior CAN.
To adjust, hold down the switches on the left seat adjustment switch group until the desired position is reached.
The left front seat adjustment control unit with memory discretely actuates, depending on the request, the following motors in the left front seat adjustment motor group with memory (M27):
- forward/back motor (M27m1)
- rear raise/lower motor (M27m2)
- front up/down motor (M27m3)
- head restraint raise/lower motor (M27m4)
- backrest forward/back motor (M27m5)
- seat cushion forward/back motor (M27m6)
Saving and retrieving seat positions
Additional function requirements
- Normalized electric seat adjustment
Store driver seat position function sequence
There are 2 button operation options for storing the seat position:
- the memory switch (S91/2s9) is held depressed and then memory 1 switch (S91/2s6), the memory 2 switch (S91/2s7), or the memory 3 switch (S91/2s8) is pressed for the particular memory,
- Press the memory switch for t > 100 ms. Within t ≤ 3 s, the memory 1 switch, the memory 2 switch, or the memory 3 switch must then be pressed for the particular memory.
Successful storage of the seat position is acknowledged by the instrument cluster (A1) with an acknowledgment tone.
The status of the switches is read in by the door control unit and transmitted to the left front seat adjustment control unit with memory via interior CAN. The left front seat adjustment control unit with memory stores the current seat position.
Move to stored position, function sequence
To be able to move to a stored seat position, the memory 1 switch, the memory 2 switch, or the memory 3 switch must be held depressed until the stored end position has been reached. If the switch is released, the adjustment procedure is terminated immediately.
Abort conditions
Moving to a stored position is interrupted when:
- Manual seat adjustment
- Manual mirror adjustment (only driver)
- Manual steering column adjustment (only driver)
- When additional memory switches are pressed
Head restraint presetting
Additional function requirements
- Normalized seat fore/aft position
- Normalized head restraint height
Function sequence
The height of the head restraint is preset automatically by the left front seat adjustment control unit with memory depending on the seat fore/aft position. If the seat is adjusted forward, the head restraint moves down. If the seat is adjusted rearward, the head restraint moves up. The head restraint is adjusted in 4 steps. To allow a minor correction of the longitudinal adjustment without changing the head restraint adjustment, the head restraint drive is not actuated until a longitudinal adjustment of approx. 15 mm is made.
The head restraint adjustment by pressing the operating switch or adjusting a stored position are independent of the "head restraint presetting" function.
Synchronizing
Additional function requirements
- Circuit 15R ON
Function sequence
Normalization is important for the assignment of the absolute adjustment position and the position recorded by the left front seat adjustment control unit with memory. Normalization must be performed during initial startup or in a denormalized condition.
To carry out the normalization procedure, it is necessary to move to the following mechanical end stops:
- Front end stop of fore/aft adjustment, backrest adjustment, and seat cushion adjustment
- Downstop of inclination adjustment, height adjustment, and head restraint adjustment
For normalization, the corresponding switch in the left 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 switches off the corresponding seat adjustment motor.
The normalization can also be performed via diagnosis. In this case, circuit 15R must be switched on.
An adjustment is denormalized, if the signal of the corresponding Hall sensor is not received. The Hall sensors are allocated to the particular adjustment motors. The denormalization procedure can also be performed via diagnosis.
Position measurement
The adjustment motors are equipped with Hall sensors. The signals from the Hall sensors are read in and evaluated by the left front seat adjustment control unit with memory.
Anti-lock device
If a motor is blocked during one of the adjusting functions triggered by the operating switch or while setting to a stored position, it is switched off after approx. 2.5 s. Re-enabling in the same adjusting direction is not permitted until the switch has been released for approx. 2.5 s. Re-enabling in the opposite direction is possible immediately.
Collision avoidance
A collision of the seat cushion frame with the seat adjuster, the center console, the B-pillar, or the roof is prevented via performance maps stored in the left front seat adjustment control unit with memory.
The following collisions may occur when adjusting the seat depending on the current seat position:
Rear compartment access
To make it easier to access the rear boxes in the rear compartment, the driver and the front passenger seat can be moved electrically to the front end stop position. In the process, the backrest is also moved to the front end stop, and the head restraint is lowered.
Moving the front seat forward and folding it down
The pressed left rear compartment access switch (S137) is read in by the left front seat adjustment control unit with memory.
Then the
- Fore/aft motor
- Head restraint up/down motor
- Backrest fore/aft motor are actuated at the same time.
The motors remain actuated until the limit stops of head restraint, backrest, and fore/aft adjustment have been reached.
Moving the front seat backward and folding it down toward the back
The same procedure is used as for moving forward and folding down toward the front by pressing the left rear compartment access switch. In the process, the seat and the backrest are moved to the initial position, and then the head restraint is moved to its previous position.
The fore/aft adjustment to allow access to the rear compartment is moved to the particular end position with twice the speed.
Abort conditions
- Pressing a switch of the left seat adjustment switch group
- Hall sensor of fore/aft or backrest adjustment and head restraint recognized to be defective
- Circuit 15 ON and vehicle speed v ≥ 5 km/h
- Repeat pressing the left rear compartment access switch
