GF91.29-P-0004GM Electric Seat Adjustment (ESA) Function

GF91.29-P-0004GM Electric Seat Adjustment (ESA) 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 undervoltage (U < 9.3 V)

Function description of electric seat adjustment (ESV [ESA]), general
On vehicles with code (275) Memory package (driver seat, steering column, mirrors) the driver seat and on vehicles with code (242) Electrically adjustable front passenger seat with memory also the front passenger seat can be electrically adjusted as follows:
- Seat fore/aft position
- Backrest angle
- Seat height
- Seat inclination
- Head restraint height

The electric seat adjustment (ESA [ESV]) is described on the driver seat for left-hand drive vehicles as an example, however this also applies for the front passenger seat.

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 electric 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 various adjustments are received in a group by the driver-side front seat adjustment control unit with memory (N32/1), then the adjustment request with the higher priority is executed.

The priorities are determined as follows:
Group 1
Priority high, backrest adjustment
Priority average, head restraint
Priority low, inclination adjustment

Group 2
Priority high, fore/aft adjustment
Priority average, height adjustment

Fault handling
The driver-side front seat adjustment control unit with memory checks the requests received for seat adjustments for plausibility. Correct requests for adjustment functions remain unaffected.

The electric seat adjustment enables the following subfunctions:
^ Manual adjustment
^ Saving and retrieving seat positions (memory function)
^ Head restraint presetting (only for vehicles as of model year 2010/change year 09 and vehicles with code (494) USA version, code (460) Canada version or code (498) Japan version)
^ Normalizing
^ Position measurement
^ Antilock device
^ 2nd seat row seat release with EASY ENTRY function and collision avoidance (model 164.8)

Described in separate subfunction
^ Folding 3rd seat row function (model 164.8 with code (845) 3rd seat row folding down electrically)

Manual adjustment
Actuation of the driver seat adjustment switch group with memory (S91) which is located on the front seat frame trim, is read in voltage-coded by the driver-side front seat adjustment control unit with memory. The driver-side front seat adjustment control unit with memory actuates the corresponding seat adjustment motor directly.

To adjust, keep switches on driver seat adjustment switch group with memory pressed down until the desired position is reached.

Depending on the request, the driver-side front seat adjustment control unit with memory actuates the following motors of the ESA [ESV] directly:
- Driver seat longitudinal adjustment motor (M27/1)
- Driver rear seat height adjustment motor (M27/2)
- Driver front seat height adjustment motor (M27/3)
- Driver head restraint motor (M27/4)
- Driver backrest angle adjustment motor (M27/5)

Saving and retrieving seat positions (memory function)

Additional function requirements
^ Normalized electric seat adjustment

Store driver seat position function sequence
There are two switch operation options for storing the seat position:
- Press and hold the memory switch (S91s9) and then press the corresponding memory switch 1, 2, 3, (S91s14) for t > 40 ms.
- Press the memory switch for t > 200 ms. Memory switch 1, 2, 3 must then be pressed within 3 s.

The switches of the driver seat adjustment switch group with memory are read in directly by the driver-side front seat adjustment control unit with memory.

The driver-side front seat adjustment control unit with memory stores the current seat position.

The position of the steering column and outside mirrors are also stored on the driver side.

Successful storage of the seat position is acknowledged by the instrument cluster (A1) with an acknowledgment tone.

Move to stored position, function sequence
To move to a stored seat position, the corresponding switch on the driver seat adjustment switch group with memory has to be pressed and held until the stored seat position is reached. If the switch is released, the adjustment procedure is terminated immediately.

Abort conditions
Moving to a stored position is interrupted during:
- Manual seat adjustment
- Manual mirror adjustment (driver only)
- Manual steering column adjustment (only driver)
- Pressing additional memory switches

Head restraint presetting (only for vehicles as of model year 2010 / change year 09 and vehicles with code (494) USA version, code (460) Canada version or code (498) Japan version)

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

Function sequence
The height of the head restraint is automatically preset by the driver 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 stages. The head restraint presetting function can be switched on and off in the driver-side front seat adjustment control unit with memory using the diagnosis and is coded country-specifically using the Software Calibration Number (SCN) at the end of the assembly line.

Normalizing

Additional function requirements
^ Circuit 15R ON

The electronic ignition switch control unit (N73) transmits the circuit status via the interior CAN (CAN B).

Normalization sequence
Normalization is important for the assignment of the absolute adjustment position and the position recorded by the driver-side front seat adjustment control unit with memory. Normalization must always be performed via diagnosis when operated for the first time; however, in the denormalized condition it can also be carried out via the corresponding seat adjustment switch. To carry out the normalization procedure, it is necessary to drive to the following mechanical end stops:
- Front end stop of fore/aft adjustment and backrest adjustment
- Downstop of inclination adjustment, height adjustment, and head restraint adjustment

For normalization, the corresponding switch in the switch group for the driver seat adjustment with memory must remain actuated for t = 250 ms after the mechanical end stop has been reached. Upon successful normalization, the driver-side front seat adjustment control unit with memory switches the corresponding seat adjustment motor off.

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-side front seat adjustment control unit with memory.

Antilock device
If the signals of a Hall sensor are not received for t > 2 s, the corresponding adjustment function is switched off by the driver-side front seat adjustment control unit with memory.

It is switched on again in the same adjustment direction only after the corresponding switch in the driver seat adjustment switch group with memory is released for t ≥ 2 s. Re-enabling in the opposite direction is possible immediately.

2nd seat row seat release with EASY ENTRY function and collision avoidance (model 164.8)

Additional function requirements
- Circuit 15 OFF or
- Vehicle speed v < 5 km/h while circuit 15 ON
- Normalization of the fore/aft adjustment, height adjustment, and backrest adjustment carried out

Function sequence
The scope of the functionality is integrated in the rear SAM control unit (N10/8). The access aid microswitch for the 2nd seat row, right (S159/1) is monitored by the rear SAM control unit.

If the access aid microswitch is closed by releasing the backrest, the rear SAM control unit transmits a message to the passenger-side front seat adjustment control unit with memory (N32/2) and the instrument cluster via the interior CAN.

If the position of the front passenger seat is obstructing the folding of the seat in the second seat row, the front passenger seat is moved forwards by the passenger-side front seat adjustment control unit with memory (collision avoidance feature).

The backrest is also set in the upright position if its incline is too steep, and the seat height adjustment is moved upward to a collision-preventing position if it is set too low. If the seat adjustment has been set in front of these particular positions, an adjustment towards the rear or bottom is only possible up to these respective set positions (only for code 494 USA version).

If the armrest in the second seat row has been released, then the instrument cluster shows a corresponding message at circuit 15R ON.
As soon as the seat in the 2nd seat row has been locked again (microswitch open), the relevant message is sent to the interior CAN by the rear SAM control unit.

If the interior CAN is in bus idle mode when unlocking or locking takes place, it is awakened by the rear SAM control unit. The display extinguishes in the instrument cluster.

Abort conditions
The collision avoidance with the rear seat function is aborted upon:
- Locking of 2nd seat row rear backrest,
- Actuation of front passenger seat adjustment switch group with memory (S92).

Once the collision avoidance function with the rear seat has bee aborted, the front passenger seat can be set in any position as desired. In vehicles without code (494) USA version, a manual adjustment into the collision zone during the collision avoidance function is possible. The seat adjustment is coded following installation depending on the country.

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