GF91.29-P-0009GDA Electrical Seat Adjustment (ESA (ESE)), Function

GF91.29-P-0009GDA Electrical Seat Adjustment (ESA [ESE]), Function
- with CODE (275) Memory package (driver seat, steering column, mirrors)
- with CODE (242) Electrically adjustable front passenger seat with memory

Function requirements, general
^ No engine start (circuit 50 OFF)
^ No undervoltage (U < 9.3 V)

The electronic ignition lock control unit (N73) transmits the circuit status and the on-board electrical system voltage via the interior CAN (CAN B).

Electric seat adjustment function description, general
The electrical seat adjustment (ESA [ESE]) is described on the driver seat for left-hand drive vehicles by way of an example, but this also applies for the passenger seat.

The driver seat in vehicles with code (275) Memory package (driver seat, steering column, mirror) and also the front passenger seat in vehicles with code (242) Electrically adjustable front passenger seat with memory can be electrically adjusted as follows:
- Seat fore/aft position
- Backrest angle
- Seat height
- Seat inclination
- 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.

Fault handling
The driver seat control unit (N32/1) checks the plausibility of the seat adjustment requests that it has received. Adjustment requests for the same adjustment function in an opposite direction (e.g. backrest angle 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 (N69/1).

The ESA [ESE] provides the following subfunctions:
^ Manual setting
^ Saving and retrieving seat positions
^ Head restraint presetting (not ECE and UK)
^ Synchronizing
^ Position measurement
^ Anti-lock device

Manual setting
The manual adjustment is operated via the left front seat adjustment switch group (S22). The left front seat adjustment switch group is read in via the left door LIN (LIN B5) by the left front door control unit. The left front door control unit transmits the requests from the left front seat adjustment switch group to the driver seat control unit via interior CAN. To adjust, hold down switches on left front seat adjustment switch group until the desired position is reached.

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 several adjustment requests are received in a group by the driver seat adjustment control unit, then the adjustment request with the higher priority is executed.

The priorities are determined as follows:
Group 1
Priority high, backrest angle
Priority medium, head restraint height
Priority low, seat inclination

Group 2
Priority high, seat fore/aft position
Priority medium, seat height

The driver seat control unit actuates, depending on the request, the following ESA [ESE] motors in the rear:
- Driver seat fore/aft adjustment motor (M27/1)
- Driver seat height adjustment motor (M27/2)
- Driver seat inclination adjustment motor (M27/3)
- Driver seat head restraint adjustment motor (M27/4)
- Driver seat backrest inclination adjustment motor (M27/5)

Saving and retrieving seat positions

Additional function requirements
- ESA [ESE] normalized

Store driver seat position function sequence
There are two button operation options for storing the seat position:
- the left front memory function switch (S22s6) is held down and then the left front memory 1 switch (S22s7), the left front memory 2 switch (S22s8) or the left front memory 3 switch (S22s9) is pressed for the respective memory location
- the left front memory function switch is held down for t > 100 ms. Within 0.2 s ≤ t ≤ 3 s, left front memory 1 switch, left front memory 2 switch, or left front 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 left front door control unit via the left door LIN and transmitted to the driver seat control unit via interior CAN. The driver seat control unit stores the current seat position.

Move to stored position, function sequence
To be able to move to a stored position, left front memory 1 switch, left front memory 2 switch, or left front memory 3 switch must be held pressed until the stored end position has been reached. Releasing leads to immediate termination of the adjustment procedure.

Abort conditions
Moving to a stored position is interrupted in the event of:
- Manual seat adjustment
- Manual mirror adjustment (only driver)
- Manual steering column adjustment (driver only)
- When additional memory switches are pressed

Head restraint presetting (not ECE and UK)

Additional function requirements
- Normalized seat fore/aft position
- Normalized head restraint height

Function sequence
The height of the head restraint is adjusted automatically by the driver 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 towards the rear, the head restraint moves up. The head restraint is adjusted in stages.

The head restraint presetting function can be switched on and off in the driver seat control unit via diagnosis, and is coded via the SCN (Software Calibration Number) in a country-specific way.

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 driver seat control unit. 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 seat fore/aft position and backrest angle
- Downstop of seat inclination, seat height and head restraint height

For normalization, the corresponding switch in the left front 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 procedure should be performed via diagnosis for initial startup. 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 seat adjustment motors are equipped with Hall sensors. The signals from the Hall sensors are read in and evaluated by the driver seat control unit.

Anti-lock device
If a defective Hall sensor is detected for t > 2 s, the corresponding adjustment function is switched off by the driver seat control unit after t = 2 s.

Reactivation in the same adjusting direction is not permitted until the corresponding switch has been released for approx. t ≥ 2 s. Reactivation in the opposite adjusting direction is possible immediately.