Electrical Seat Adjustment (ESA) - GF91.29-P-0009RR
Model 190
With Code P64 (Memory package)
Function requirements, general
- No overvoltage or undervoltage
Electrical seat adjustment (ESA), general
The position of the driver and the front passenger seat can be adjusted using the ESA. The following adjustments can be made to the driver or the front passenger seat:
- Seat fore/aft position
- Backrest inclination
- Seat height
- Seat cushion inclination
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 backrest adjustment
- Low priority: seat inclination adjustment
- Group 2:
- High priority: Seat fore/aft adjustment
- Medium priority: Seat height adjustment
- Group 3:
- Medium priority: Raise/lower steering column adjustment
- High priority: Fore/aft steering column adjustment
The ESA function includes the following partial functions:
- Function sequence for position measurement
- 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 PRE-SAFE® positioning function for front passenger seat (With Code 299 (PRE-SAFE® system))
- Function sequence for collision avoidance with bulkhead
- Fault handling function sequence
Function sequence for position measurement
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. When seat adjustments are being made, 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
- Seat inclination adjustment and seat height adjustment downstop
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. The seat can only be adjusted in the same adjustment direction again after releasing the appropriate switch for t ≥ 2 s. The seat can be adjusted in the opposite direction straight away.
Function sequence for manual adjustment
Manual adjustment is done using the respective switch group, seat adjustment. Operation of the switch group, seat adjustment is read in over the door LIN by the respective door control unit. The respective door control unit sends the requests from the switch group, seat adjustment over the interior CAN to the driver seat control unit or the front passenger seat control unit. To adjust, hold down the switches in the 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, height adjustment
- Seat adjustment motor, inclination adjustment
- Seat adjustment motor, backrest inclination
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 or right memory function switch, then press memory 1, 2 or 3 switch for the relevant memory.
- Press left memory function switch or right memory function switch for t > 100 ms and then release, then press the memory 1, 2 or 3 switch for each memory within t ≥ 0.2 to 3 s.
The respective door control unit reads in the status of the switches in the switch group, seat adjustment via the door LIN and sends the "Store memory position" request 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, AMG gateway control unit and the 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 the memory switch stops the adjustment process immediately.
The respective door control unit reads in the status of the switches in the switch group, seat adjustment via door LIN and sends the "Adopt memory position" request 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 to the rear, the fore/aft adjustment, seat height adjustment and inclination adjustment are ended first and the backrest is then positioned.
When adjusting the fore/aft adjustment to the rear, the backrest adjustment to the rear and the seat height adjustment upwards, the memory setting is implemented according to the following procedure:
- Fore/aft adjustment to the rear up to the characteristic map limit, then inclination adjustment
- Stop fore/aft adjustment at characteristic map limit
- Seat height adjustment, until the memory position is reached then the inclination adjustment
- Fore/aft adjustment until memory position is reached, then inclination adjustment
- Seat backrest adjustment, until memory position is reached, then inclination adjustment
Additional function requirements for PRE-SAFE® positioning function for front passenger seat (With 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 over the chassis CAN 1, front SAM control unit and the interior CAN to the front passenger seat control unit.
Function sequence for PRE-SAFE® positioning function for front passenger seat (With 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 PRE-SAFE® adjustment request over the chassis CAN 1, front SAM control unit and the interior CAN to the front passenger seat control unit.
Detailed information is available in the separate function description for the PRE-SAFE® function.
Additional function requirements for collision avoidance with bulkhead
- ESA normalized
- The function is switched on using the diagnostic tester
Function sequence for collision avoidance with bulkhead
During seat fore/aft adjustment to the rear, seat height adjustment downwards and seat backrest adjustment backwards, collisions could occur with the bulkhead behind the front seats. To avoid this, the adjustment ranges for the seat fore/aft, height and backrest adjustments are limited by means of characteristic maps in the driver seat control unit or the front passenger seat control unit. The limit in the characteristic maps shifts depending on the height adjustment of the respective seat. If two adjustments are made in the direction of the limits in the characteristic maps, both adjustments are terminated. The rest position of the left switch group, seat adjustment or the right switch group, seat adjustment must be recognized for additional adjustment.
Collision avoidance with active seat fore/aft adjustment toward rear:
If the adjustment range limit is reached when making a seat fore/aft adjustment toward the rear, the seat backrest adjustment toward the front is activated for a specific adjustment range. If the adjustment remains active, the seat fore/aft adjustment is actuated alone up to the next adjustment range limit. This procedure alternates for as long as the seat fore/aft adjustment remains continuously actuated.
Collision avoidance with active seat backrest adjustment toward rear:
If the adjustment range limit is reached when making a backrest adjustment toward the rear, the seat backrest adjustment is stopped and only the seat fore/aft adjustment toward the front (compensation movement) is actuated for a certain adjustment range. If the adjustment remains active, then after this compensation movement, the seat fore/aft adjustment toward the front is actuated for a specific adjustment range along with the seat backest adjustment. This procedure alternates for as long as the seat backrest adjustment remains actuated.
Collision avoidance for active seat height adjustment downwards:
If the adjustment range limit is reached when making a seat height adjustment downwards, the seat backrest adjustment toward the front is activated for a specific adjustment range. If the adjustment remains active, only the seat height adjustment is actuated up to the next adjustment range limit. This procedure alternates for as long as the seat height adjustment remains actuated.
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 driver seat control unit or the front passenger seat control unit.
| Electrical function schematic for seat adjustment (ESA) | PE91.29-P-2059-97HBA | ||
| Overview of system components, electric seats | GF91.29-P-9992RR |