For 1990-2009 cars

## Lumbar Support Description and Operation With Memory A45

### Lumbar Support Components

The driver seat lumbar support system with memory (A45) consists of the following components:

• | Lumbar switch

• | Memory seat module (MSM)

• | Lumbar horizontal motor

• | Lumbar vertical motor

• | Lumbar horizontal position sensor

• | Lumbar vertical position sensor

• | MSM LOGIC/RF MASSAGE Fuse 10 A

### Lumbar Switch

Battery positive voltage is supplied at all times to the driver seat lumbar switch from the memory seat module and the MSM LOGIC/RF MASSAGE Fuse located in the rear fuse block. When the lumbar switches are pressed they send a 12-volt signal to the memory seat module (MSM). The MSM then commands the lumbar motors to move in response to the switch signals.

### Motors

The lumbar support system consists of 2 motors, horizontal and vertical, that operate independently of each other. Each motor contains a electronic circuit breaker (PTC), which will reset only after voltage has been removed from the motor. The lumbar horizontal motor moves the lumbar support in the forward or rearward directions while the lumbar vertical motor moves the lumbar support in the up or down directions. The MSM controls both lumbar motors via half bridges that are connected to a single power rail internal to the module. The MSM connects all lumbar motor outputs on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The MSM checks to see if this reference voltage is shorted to ground or battery before enabling any seat or lumbar motor.

Soft stop functions are not used for driver seat motors that are controlled by either a memory or non-memory MSM.

### Lumbar Horizontal Movement

When the lumbar switch is operated to move the lumbar support forward, battery positive voltage is applied through the switch contacts and the driver seat lumbar forward switch signal circuit to the memory seat module (MSM). In response to this signal, the MSM applies battery positive voltage through the lumbar motor forward control circuit and ground through the lumbar motor rearward control circuit to the motor. The motor runs to drive the lumbar support forward toward the occupant's back until the switch is released. Moving the lumbar support rearward works similarly to moving the lumbar support forward, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction. The MSM also controls the lumbar horizontal motor during memory recall functions.

### Lumbar Vertical Movement

When the lumbar switch is operated to move the lumbar support up, battery positive voltage is applied through the switch contacts and the lumbar up switch signal circuit to the memory seat module (MSM). In response to this signal, the MSM applies battery positive voltage through the lumbar motor up control circuit and ground through the lumbar motor down control circuit to the motor. The motor runs to drive the lumbar support up until the switch is released. Moving the lumbar support down works similarly to moving the lumbar support up, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction. The MSM also controls the lumbar vertical motor during memory recall functions.

### Lumbar Position Sensors

The lumbar position sensors are potentiometers which are an internal part of each lumbar motor. The memory seat module (MSM) supplies a 5-volt reference voltage through the 5-volt reference circuit and ground through the low reference circuit to each lumbar position sensor. When the lumbar motor rotates, the resistance of the potentiometer varies changing the feedback voltage of the position sensor signal circuit. This voltage varies from 0.27-4.65 volts. The MSM monitors this voltage signal to determine the lumbar position.

When a memory set command is received, the MSM records the lumbar position by storing the feedback voltage from each position sensor. Then when a memory recall command is received, the MSM moves the motors until the position sensor feedback voltages equals the feedback voltages stored in memory. The lumbar support is not involved in the easy exit function.

### Memory Functions

Refer to Memory Seats Description and Operation.

## Lumbar Support Description and Operation Without Memory A45

### Lumbar Support Components

The front passenger power seat lumbar support systems consist of the following components:

• | Lumbar switch

• | Lumbar horizontal motor

• | Lumbar vertical motor

• | MSM/RT FRT PWR SEAT Circuit Breaker 25 A

### Lumbar Switch

The lumbar switch provides both power and ground to the selected lumbar motors. Battery positive voltage is supplied at all times to the front passenger seat lumbar switch from the MSM/RT FRT PWR SEAT Circuit Breaker located in the rear fuse block. Ground for the lumbar adjuster switch is supplied from the G300 ground stake.

### Lumbar Motors

The lumbar support system consists of two lumbar motors, horizontal and vertical, that operate independently of each other. Each motor contains an electronic circuit breaker (PTC) that will reset only after voltage has been removed from the motor. The lumbar horizontal motor moves the lumbar support forward and rearward and the lumbar vertical motor moves the lumbar support up and down.

### Horizontal

When the lumbar switch is operated to move the lumbar support rearward, battery positive voltage is applied through the lumbar rearward switch contacts and the lumbar motor rearward control circuit to the lumbar horizontal motor. The motor is grounded through the lumbar forward switch contacts and the lumbar motor forward control circuit to the horizontal motor. The motor runs to drive the lumbar support rearward away from the occupant's back until the switch is released. Moving the lumbar support forward works similarly to moving the lumbar support rearward, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

### Vertical

When the lumbar switch is operated to move the lumbar support up, battery positive voltage is applied through the lumbar up switch contacts and the lumbar motor up control circuit to the lumbar vertical motor. The motor is grounded through the lumbar down switch contacts and the lumbar motor down control circuit to the vertical motor. The motor runs to drive the lumbar support up until the switch is released. Moving the lumbar support down works similarly to moving the lumbar support up, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.