Lumbar Support Description and Operation without Memory-A45

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

The lumbar switch provides both power and ground to the lumbar motor. Battery positive voltage is supplied at all times to the lumbar adjuster 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.

The lumbar support system consists of a lumbar horizontal motor. The 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.

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.

Lumbar Support Description and Operation with Memory-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 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 motor to move in response to the switch signals.

The lumbar support system consists of the lumbar horizontal motor. The 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. The MSM controls the lumbar motor via a half bridge that is connected to a single power rail internal to the module. The MSM connects both 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.

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.

The lumbar position sensor is a potentiometer which is an internal part of the 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 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 0.27-4.65 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 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.