For 1990-2009 cars

## Lumbar Support Description and Operation with A45 enabled

### 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

• | DPM Fuse 10 A

The memory seat module (MSM) is referenced in the Tech 2 as the driver position module (DPM).

### Lumbar Switch

Battery positive voltage is supplied at all times to the driver seat lumbar switch from the DPM Fuse located in the left 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 inputs.

### Motor

The lumbar support system consists of 2 motors, horizontal and vertical, that operate independently of each other. 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. Each motor contains an electronic circuit breaker (PTC). It opens in the event of a circuit overload and will reset only after voltage has been removed from the circuit.

Soft stop functions are not used for driver seat motors that are controlled by either a memory or non-memory MSM. However, soft stop functions are used for the MSM controlled steering column motors. Refer to Steering Wheel and Column Description and Operation.

### 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 MSM. In response to this signal, the MSM applies battery positive voltage through the lumbar motor forward control circuit and ground through the driver seat horizontal motor rearward control circuit to the motor. The motor runs to drive the lumbar support forward toward the occupants back until the switch is released. Moving the entire seat rearward works similarly to moving the lumbar support forward, except that battery positive voltage and ground are applied on 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 driver seat lumbar up switch signal circuit to the MSM. In response to this signal, the MSM applies battery positive voltage through the lumbar motor up control circuit and ground through the driver seat horizontal motor down control circuit to the motor. The motor runs in order to drive the lumbar support up until the switch is released. Moving the entire seat 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. The MSM also controls the lumbar vertical motor during memory recall functions.

### Lumbar Position Sensor

The lumbar position sensors are potentiometers which are an internal part of each lumbar motor. The 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 0.25-4.75 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 feed back 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.

### Position Memory Functions

Refer to Memory Seats Description and Operation.

## Lumbar Support Description and Operation without A45

### Lumbar Support Components

The passenger seat lumbar support system consists of the following components:

• | Lumbar Switch

• | Lumbar Horizontal Motor

• | Lumbar Vertical Motor

• | PWR SEAT Circuit Breaker 30 A

• | RR LUM/ANT Fuse 20 A

### Lumbar Switch

Battery positive voltage is supplied at all times to the passenger seat lumbar switch from the PWR SEAT Circuit Breaker located in the rear fuse block. The lumbar switch is grounded through the switch ground circuit and G30. The lumbar switch provides both power and ground to the selected lumbar motors.

### Motor

The lumbar support system consists of 2 lumbar 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 up or 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 motor. The motor is grounded through the lumbar forward switch contacts and the lumbar motor forward control circuit. 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. The motor runs in order to drive the lumbar support up until the switch is released. Moving the entire seat 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.

## Lumbar Support Description and Operation with A45 disabled

### Lumbar Support Components

The driver seat lumbar support system with a nonmemory configured memory seat module (MSM) consists of the following components:

• | Lumbar Switch

• | Memory Seat Module (MSM)

• | Instrument Panel Module (IPM)

• | Lumbar Horizontal Motor

• | Lumbar Vertical Motor

• | Lumbar Horizontal Position Sensor

• | Lumbar Vertical Position Sensor

• | DPM Fuse 10 A

The memory seat module (MSM) is also referenced as the driver position module (DPM) for this vehicle.

### Non Memory Driver Memory Seat Module and IPM

The non-memory version of the driver power seat and lumbar still includes the Memory Seat Module (MSM). The RPO codes for seating are A45 for memory and AL2 for lumbar. The instrument panel module (IPM) contains a configuration frame for the vehicle RPOs that is configured according to each vehicle RPO content. In order for the MSM to determine the memory configuration it looks for 2 signals via GMLAN serial data from the IPM to determine the seating RPO content. These signals are Memory Seat Present (A45) and Memory Lumbar Present (AL2). When these signals are FALSE, the seat is non memory, and the MSM will not receive signals from the seat position sensors. However, the MSM always receives column position sensor signals. Refer to Steering Wheel and Column Description and Operation.

### Lumbar Switch

Battery positive voltage is supplied at all times to the driver seat lumbar switch from the DPM Fuse located in the left 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 inputs.

### Motor

The lumbar support system consists of 2 motors, horizontal and vertical, that operate independently of each other. 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. Each motor contains a positive temperature coefficient (PTC) circuit breaker that opens in the event of a circuit overload and will reset only after voltage has been removed from the circuit.

Soft stop functions are not used for driver seat motors that are controlled by either a memory or non-memory MSM. However, soft stop functions are used for the MSM controlled steering column motors. Refer to Steering Wheel and Column Description and Operation.

### 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 MSM. In response to this signal, the MSM applies battery positive voltage through the lumbar motor forward control circuit and ground through the driver seat horizontal 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 entire seat rearward works similarly to moving the lumbar support forward, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

### 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 driver seat lumbar up switch signal circuit to the MSM. In response to this signal, the MSM applies battery positive voltage through the lumbar motor up control circuit and ground through the driver seat horizontal motor down control circuit to the motor. The motor runs in order to drive the lumbar support up until the switch is released. Moving the entire seat 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.