Electric seat adjustment (ESA) function - GF91.29-P-0004GZ: Notes
MODEL 164, 251 with CODE (275) Memory package (driver seat, steering column, mirrors) with CODE (242) Electrically adjustable front passenger seat with memory
Shown on model 164.8
The electric seat adjustment (ESA [ESV]) is made up of the following component functions:
Normalize seat adjustment.
Normalize seat adjustment.
- Normalize seat adjustment.
- Position detection
- Blockage detection
- Head restraint presetting
(up to 31.5.07, not Economic Commission for Europe (ECE))
Further partial functions are described in separate documents:
- Adjust front seat
- Save and call up seat position of front seats
- Easy entry/exit feature for driver seat
- Seat release for 2nd seat row (model 164.8, model 251)
- Folding 3rd seat row
(model 164.8 with code (845) 3rd seat row folding down electrically)
Normalization is important for the assignment between the actual adjustment position and the position recorded by the front seat adjustment position and the position recorded by the front seat adjustment control unit. Normalization must be performed during initial startup or in a denormalized condition.
The assignment is conducted by moving to the following end stops:
- Longitudinal adjustment, front stop
- Inclination adjustment, lower stop
- Height adjustment on lower stop
- Backrest adjustment, front stop
- Head restraint adjustment, lower stop
Upon reaching each end stop the adjustment request must remain pending for another 250 ms.
The front seat adjustment control unit recognizes each end stop due to the lack of signals from the Hall sensors integrated into the motors and switches off the corresponding motor. The location counter in the front seat adjustment control unit is reset to zero.
An adjustment is denormalized if the signal from the Hall sensor fails or the mechanical stop is exceeded.
Position recognition
Function requirements:
- Seat adjustment normalized
Position recognition function
The Hall sensor signals are counted in the location counter of the seat adjustment control unit. Depending on the motor's actuation voltage they are evaluated as either positive or negative.
Lockup recognition
Function requirement
- Seat adjustment normalized
Blockage detection function
If during an active adjustment function there are no Hall sensor signals (e.g. seat mechanism blocked), the corresponding adjustment function is switched off after t = 2 s by the front seat adjustment control unit. 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.
Head restraint presetting
Function requirement
- Seat adjustment normalized
- Circuit 15R ON or
respective front door open
Head restraint presetting function
The position of the head restraint is preset automatically by the relevant seat adjustment control unit to match the longitudinal adjustment position. The head restraint presetting function can be switched on and off using STAR DIAGNOSIS.
| Block diagram of electric seat adjustment (ESA [ESV]) | GF91.29-P-0004-03GZ | |
| Seat adjustment, function | GF91.29-P-2005GZ | |
| Save/call up seat position, function | GF91.29-P-2006GZ | |
| Easy entry/exit feature driver seat, function | GF91.29-P-2014GZ | |
| Seat release in 2nd seat row, function | Model 164.8 | GF91.29-P-2017GZ |
| Folding 3rd seat row, function | Model 164.8 with code (845) 3rd seat row folding down electrically | GF91.29-P-2018GZ |