Electric seat adjustment (ESA) function (with CODE 275) - GF91.29-P-0004CWA

MODEL 204.0 /2 with CODE (275) Memory package (driver seat, steering column, mirrors) with CODE (242) Electrically adjustable front passenger seat with memory up to Model Year 8 

General 

The driver seat in vehicles with code (275) Memory package (driver seat, steering column, mirrors) and the front passenger seat in vehicles with code (242) Electrically adjustable front passenger seat with memory are electrically adjusted as follows:

• Longitudinal seat position
• Backrest angle
• Seat height
• Seat inclination
• Head restraint height

The storage and retrieval of the respective seat position is also possible.

Function requirements 

• Electric seat adjustment (ESA [ESV]) operational
• 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 power supply voltage via the interior CAN.

The ESA provides the following subfunctions: 

• Manual adjustment
• Storage and retrieval of seat positions
• Head restraint presetting (only , and )
• Normalization
• Position measurement
• Anti-lock device

Manual adjustment 

Driver seat function sequence 

The manual adjusting facility 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 by the left front door control unit (N69/1). The left front door control unit transmits the switch group requests to the driver seat control unit via the interior CAN (N32/1).

Depending on the request, the driver seat control unit actuates the following ESA motors:

• 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)

Front passenger seat function sequence (with code (242) Electrically adjustable front passenger seat with memory) 

The manual adjustment facility is operated via the right front seat adjustment switch group (S23). The right front seat adjustment switch group is read in via the right door LIN by the right front door control unit (N69/2). The right front door control unit transmits the switch group requests to the front passenger seat control unit via the interior CAN (N32/2).

Depending on the request, the front passenger seat control unit actuates the following ESA motors:

• Front passenger seat fore/aft adjustment motor (M28/1)
• Front passenger seat height adjustment motor (M28/2)
• Front passenger seat inclination adjustment motor (M28/3)
• Front passenger seat head restraint adjustment motor (M28/4)
• Front passenger seat backrest inclination adjustment motor (M28/5)

Storage and retrieval of seat positions 

Additional function requirements 

• ESA normalized

Store driver seat position function sequence 

The left front memory function switch (S22s6) and then the left front memory 1 switch (S22s7), the left front memory 2 switch (S22s8) or the left front memory 3 switch (S22s9) for the relevant storage location must first be operated in order to do this.

Storage of the seat position is confirmed by the instrument cluster (A1) with an acknowledgment tone.

The status of the switches is read in via the left door LIN by the left front door control unit and transmitted to the driver seat control unit via the interior CAN. The driver seat control unit stores the current seat position.

Store front passenger seat position function sequence (with code (242) Electrically adjustable front passenger seat with memory) 

The right front memory function switch (S23s6) and then the right front memory 1 switch (S23s7), the right front memory 2 switch (S23s8) or the right front memory 3 switch (S23s9) for the relevant storage location must first be operated in order to do this. Storage of the seat position is confirmed by the instrument cluster with an acknowledgment tone.

The status of the switches is read in via the right door LIN by the right front door control unit and transmitted to the front passenger seat control unit via the interior CAN. The front passenger seat control unit stores the current seat position.

Move to stored position function sequence 

In order to move to a previously stored position, the relevant memory switch must be operated until the stored position has been reached. The adjusting procedure stops immediately as soon as the switch is released.

Head restraint presetting 

additional function requirements 

• Normalized longitudinal seat position
• Normalized head restraint height

Function sequence 

The height of the head restraint is preset automatically by the driver seat control unit depending on the longitudinal seat position. If the seat is moved forwards, the head restraint moves down. If the seat is moved backwards, the head restraint moves up. The head restraint is adjusted in stages.

Head restraint presetting can be disabled using STAR DIAGNOSIS.

Synchronizing 

Function sequence 

Normalization is important for the assignment between the absolute adjustment position and the position recorded by the driver or front passenger seat control unit. Normalization must be performed during initial start-up or in a denormalized condition.

The following mechanical end stops must be moved to in order to perform normalization:

• front longitudinal adjustment and backrest adjustment end stops
• lower inclination adjustment, height adjustment and head restraint adjustment end stops

In order to perform normalization, the relevant switch in the relevant seat adjustment switch group must continue to be pressed for t = 250 ms after the mechanical end stop has been reached.

If normalization has been successful, the driver seat control unit or the front passenger seat control unit switches the relevant seat adjustment motor off.

The normalization can also be carried out using STAR DIAGNOSIS.

An adjustment is denormalized if no signal is received from the relevant Hall sensor.

Position measurement 

The seat adjustment motors are equipped with Hall sensors. The Hall sensor signals are read in and evaluated by the driver seat control unit or the front passenger seat control unit.

Anti-lock device 

If a Hall sensor signal is not received for t > 2 s, the relevant adjusting function is shut off by the driver seat or front passenger seat control unit.

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

	Electrical function diagram for seat adjustment (ESA [ESV])		PE91.29-P-2050-99FAA
	Electric seat adjustment (ESA [ESV]), location of components		GF91.29-P-0004-01CWA
	Block diagram of electric seat adjustment (ESA [ESV])		GF91.29-P-0004-03CWA
	Seat adjustment motor component description	M27/1, M27/2, M27/3, M27/4 and M27/5; M28/1, M28/2, M28/3, M28/4 and M28/5 (with code (242) Electrically adjustable front passenger seat with memory)	GF91.29-P-5213CW
	Driver seat control unit component description	N32/1	GF91.29-P-5231CW
	Front passenger seat control unit component description	N32/2 On vehicles with code (242) Electrically adjustable front passenger seat with memory	GF91.29-P-5241CW
	Left front door control unit, component description	N69/1	GF72.29-P-6001CW
	Right front door control unit, component description	N69/2	GF72.29-P-6009CW
	Electronic ignition lock control unit, component description	N73	GF80.57-P-6001CW
	Seat adjustment switch group component description	S22; S23 (with code (242) Electrically adjustable front passenger seat with memory)	GF91.29-P-5206CW