Lumbar Support Description and Operation w/o A45

The driver and passenger seat lumbar support systems each consist of the following components:

The power lumbar switches provide both power and ground to the lumbar motor. Battery positive voltage is supplied at all times to the driver and passenger seat lumbar switch from the SEATS Circuit Breaker located in the left rear fuse block. Both lumbar switches are grounded through the switch ground circuit and G 307.

The lumbar support system consists of one motor that moves the lumbar support horizontally forward or rearward. The motor contains an electronic circuit breaker (PTC) that opens in the event of a circuit overload and will reset only after voltage has been removed from the circuit.

When the lumbar switch is operated to move the lumbar support forward, battery positive voltage is applied through the switch contacts and the lumbar motor forward control circuit to the motor. The motor is grounded through the lumbar rearward switch contacts and 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 opposite circuits causing the motor to run in the opposite direction.

Lumbar Support Description and Operation with A45

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

Battery positive voltage is supplied at all times to the driver seat lumbar switch from the SEATS Fuse located in the left rear fuse block. When the lumbar switches are pressed they send a 12 volt signal to the MSM. The MSM then commands the lumbar motor to move in response to the switch signals.

The lumbar support system consists of one motor that moves the lumbar support horizontally forward or rearward. The motor contains a electronic circuit breaker (PTC) that opens in the event of a circuit overload and will reset only after voltage has been removed from the circuit. The memory seat module provides the motor with a soft stop that will actually stop the motor just before its physical end-of-travel. This decreases the stress on the motor. If the motor reaches it's end-of-travel due a soft stop and the switch is released and pressed again, the lumbar support will move short distance farther to it's physical travel limit.

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 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.

The lumbar position sensor is a potentiometer which is attached directly to the lumbar motor. The MSM supplies a 5 volt reference voltage through the 5 volt reference circuit and ground through the low reference circuit to the 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 feedback voltage from the position sensor. Then, when a memory recall command is received, the MSM moves the motor until the position sensor feedback voltage equals the feedback voltage stored in memory. The lumbar support is not involved in the easy exit function.

Refer to Memory Seats Description and Operation .