General Information
Seat/Mirror/Steering Column Memory
Purpose of the System
The front seats, outside rear/view mirrors and steering column (if equipped) positions are electrically adjustable. The "customized" adjustment positions can be memorized and stored for three different users and recalled back to the individual position is (with the exception of the passenger seat - not in memory).
The basic features of seat/mirror/steering column operation, as well as the memory positions is integrated into the ZKE III system.
Inputs - Processing - Outputs
System Components:
- Seat/Steering Column Memory Module (PM SM).
- Driver's Door Switchblock Module (PM FT/SB - early E38 was separate).
- Passenger's Door Module (PM BT - E53 combined with window switch).
- General Module (GM III).
- 3 Position Memory Switch.
- Seat Switch.
- Steering Column Switch.
- Seat/Steering Column/Mirror Motors.
The Seat/Steering Column Memory Module communicates with the DISplus or MoDiC for diagnosis and Vehicle Memory encoding.
System Components - with Principle of Operation
Manual Operation: The manual adjustments of the seat, mirrors and steering column are carried out with the respective switches as with the previous systems.
The mirror adjustment switch is located in the driver's switch block. The mirror operation input is a digital signal that is processed by each respective module for mirror positioning.
Memory Storage: The parameters for storing memory positions are are as follows:
- With the transmission range selector in "P" and the mirror change over switched to the left, switch the ignition on and press the "M" on the memory switch.
- The memory indicator lamp switches on for 7 seconds.
- Press one of the three position switches (1, 2 or 3) within the 7 second memory period.
- The current positions of the mirrors, seat and steering column are stored for recall.
The positions of the mirrors are stored in the respective door modules based on the position of the feedback potentiometers. The positions of the seat and steering column are stored in the seat module, based on the ripple count.
Recalling a memory position setting is possible by either pressing and holding the recall switch (1, 2 or 3) with KL 15 "ON" or tapping the recall button (1, 2 or 3) with:
- The driver's door open and KL 15 "OFF".
- KL R ON and KL 15 "OFF".
The recall movement can be interrupted at any time by touching any of the adjusting switches.
Mirror
Principle of Operation
The output stages and memory storage of mirror positions is handled by the respective door modules. The positioning of the mirrors is signaled from the driver's door switch block/module. The signal passes over the P-Bus to the passenger's door module.
The memory/recall for the driver's mirror comes directly into the door module from the memory switch. The operation for the passenger's side mirror is carried out over the P-Bus from the driver's door module to the passenger's module.
The memory positions are stored in each respective module. The memory position is recognized by the feedback potentiometers located on each mirror motor.
The reverse gear tilt feature for the passenger's mirror is signaled from the GM, over the P-bus, when reverse is selected and the mirror switch is set for the driver's side.
Mirror heating is controlled by each respective door module. The GM receives the outside temperature from the IKE and passes it to the door modules. The "ON" time for mirror heating is adjusted based on the outside temperature.
A pulsed heating cycle is used for the mirrors based on the outside temperature.
System Components: Inputs - Processing - Outputs
Driver's Seat (E38/E39)
Principle of Operation
Each motor for seat adjustment contains a micro-processor (called a Ripple Counter) that receives a digital signal from the seat control module for motor activation. The motors are connected to KL 30 and KL 31 and respond to the signals generated by the seat module when seat movement is requested. The seat adjustment switch provides ground input signals to the module when seat movement is desired. The module processes these input signals and sends output signals to the seat motor processors. The seat motor processors activate the motors and the seat moves to the desired point.
The circuitry of the Ripple Counter detects the motor activation current As the armature segments of the motor rotate passed the brushes, the current flow rises) and falls producing a ripple effect.The peaks of these ripples are counted and stored in the Ripple Counter module. The memory function of the seat module uses this ripple count instead of feedback potentiometers to memorize and recall seat positions.
Ripple Count Recognition
When the seat is installed and the battery is connected, the ripple counter uses the initial position of the motors as the "Zero Position".
Any movement from this point is counted as "+" or "-" pulses as the motors move in either direction.
The pulse position of the motors is stored in the seat module, in an EEPROM (of the PM-SM), before the ZKE goes into its "Sleep Mode".
This prevents the position recognition from being lost. If the battery is disconnected before the 16 minute sleep mode activation, the memory positions of the seat will be lost and reprogramming will be required.
Diagnosis: The PM-SM communicates with the DISplus or MoDiC. The PM-SM monitors the seat motors and circuits as well as it's internal operation. Any detected faults are stored in the PM-SM fault memory and are called up when diagnosing the system with the Fault Symptom diagnostic plan. The PM-SM also provides status display to the DISplus of the input and output control signals as well as component activation.
Passenger's Seat (without memory)
Principle of Operation
The passenger seat control switch is purely a mechanical switching module that activates the passenger seat motors without position monitoring capabilities. Due to the limited operation requirements, the passenger seat control switch is not equipped with on board diagnostics.
The Passenger Seat control switch is equipped with an overload protection function. If excessive amperage is drawn due to a defective motor or a switch is stuck driving a motor to the end limit, the function activates opening the motor control circuit.
Passenger Seat Motors: Each motor is individually controlled by the Seat Control Switch. Each position motor is connected to the seat position switch by a two wire circuit providing motor activation in both directions (no position recognition).
Passenger Seat Adjustment: Operation of the passenger seat is always possible regardless of the ignition key position. Moving a position switch operates a the motor control contacts directly, the switch applies voltage and ground path directly to operate the motor. Reversing the switch simply changes the motor polarity. More than one passenger seat motor can be run simultaneously.
Optional Seat Back Lumbar Support
The optional air bladder lumbar support system is similar in all vehicles (if equipped). Each seat contains the following components:
- Four position circular rocker switch in the seat base trim in the area of the seat switches.
- Electrically controlled air compressor with over pressure cut out under each seat.
- Two solenoid activated air controlling valve blocks (one per air bladder). Each valve block includes an inlet and an outlet valve. When energized they direct air into the bladder(s) to inflate or relieve trapped air to deflate the bladders.
- Connecting hoses and air bladders in lower seat back.
Principle of Operation
The lumbar support system can be operated at any time regardless of key position. The four position circular rocker switch provides power switching to operate the system as follows:
- Position 1: The internal switch contacts provide a power and ground path for both valve block inlet valves and the air compressor. Both bladders inflate until the switch is released. If the switch is held continuously, an overpressure bypass valve opens on the compressor preventing damage to the bladders.
- Position 2: Compressor activated, upper bladder inflates, lower bladder deflates.
- Position 3: Compressor activated, lower bladder inflates, upper bladder deflates.
- Position 4: Compressor is not activated. Upper and bower bladders both deflate.
This function is not stored in memory for recall.
Diagnosis
The seat lumbar support system is purely electro-pneumatic control system. No electronic diagnostic communication is possible.