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

GF91.29-P-0004RC 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 engine start (circuit 50 OFF)
^ No undervoltage (U < 9.3 V)

The EIS [EZS] control unit (N73) transmits the circuit status and the on-board power supply voltage via interior CAN.

Electric seat adjustment function description, 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 driver seat on vehicles with code (275), and also the front passenger seat on vehicles with code (242), can be adjusted electrically as follows:
- Seat fore/aft position
- Backrest angle
- Seat height
- Seat inclination

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-side front seat adjustment control unit with memory checks the requests received for seat adjustments for plausibility. Adjustment requests for the same adjustment function in an opposite direction (e.g. backrest adjustment forward//back simultaneously) are rejected. Correct requests for other adjustment functions remain unaffected.

The electric seat adjustment enables the following subfunctions:
^ Manual adjustment
^ Saving and retrieving seat positions
^ Synchronizing
^ Position measurement
^ Anti-lock device

Manual adjustment
The manual adjustment is operated via the left seat adjustment switch group (S22). The left seat adjustment switch group is read in directly by the driver-side front seat adjustment control unit with memory. To adjust, hold down switches in left seat adjustment switch group until the desired position is reached.

Priorities
The seat adjustment is divided up into 2 groups and 2 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 low, inclination adjustment

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

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

Saving and retrieving seat positions

Additional function requirements
^ Normalized electric seat adjustment

Store driver seat position function sequence
There are two button operation options for storing the seat position:
- The memory switch (S22s6) is held, then one of the memory buttons 1, 2, 3 (S22s7) is pressed for the corresponding memory
- Press the memory switch for t > 100 ms. Then one of the memory buttons 1, 2, 3 must be pressed for the corresponding memory within 0.2 s ≤ t ≤ 3 s

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

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

Function sequence for moving to stored position
To move to a stored position, one of the memory buttons 1, 2, 3 has to be pressed and held until the stored end position is reached. If the switch is released, the adjustment procedure is terminated immediately.

Abort conditions
Moving to a stored position is interrupted:
- By manual seat adjustment
- By manual mirror adjustment (driver only)
- By manual steering column adjustment (driver only)
- When additional memory switches are pressed

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 fore/aft adjustment and backrest adjustment
- Downstop of inclination adjustment and height adjustment

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-side front seat adjustment control unit with memory switches the corresponding seat adjustment motor off.

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-side front seat adjustment control unit with memory.

Anti-lock device
If a defective Hall sensor is detected for t > 2 s, the corresponding adjustment function is switched off by the driver-side front seat adjustment control unit with memory 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. Re-enabling in the opposite direction is possible immediately.