System Operation

Seating - Power-Fold

System Operation

System Diagram





Network Message Chart

BCM (Body Control Module) Network Input Messages







Seating - Power-Fold

The third row power seat system includes the following components:
- Third row power seat relay
- PFSM (Power-Fold Seat Module)
- Seat control switch
- Power-stow seat motor assembly (contains LH (Left Hand) and RH (Right Hand) motors and sensors)
- LH (Left Hand) and RH (Right Hand) power-fold seat motor and sensor assemblies (backrest)
- LH (Left Hand) and RH (Right Hand) latch assemblies (contains latch motor and latch switch)

The third row power seat relay coil receives voltage from the battery saver relay in the BCM (Body Control Module) (courtesy lamp circuit) and ground from the chassis. When energized, the relay switch closes and supplies battery voltage from the BJB (Battery Junction Box) to the PFSM (Power-Fold Seat Module). Sufficient battery voltage is required for PFSM (Power-Fold Seat Module) operation. If battery voltage drops below 8 volts, a started seat movement stops.

When the gear selector lever is in the PARK position and the liftgate is open, the BCM (Body Control Module) supplies voltage to the PFSM (Power-Fold Seat Module) enable circuit for 30 minutes. With the ignition OFF, the BCM (Body Control Module) disables the battery saver relay after 10 minutes. The system can be re-enabled by opening any door, pressing the unlock button on the RKE (Remote Keyless Entry) transmitter or turning the ignition ON. A short to voltage on the PFSM (Power-Fold Seat Module) enable circuit can result in the third row power seat being operational any time the battery saver relay is energized, regardless of gear selector lever or tailgate position.

The seat control switch contains the seat selector switch button and seat position switch buttons. The PFSM (Power-Fold Seat Module) receives a voltage signal from the seat selector switch for 3 modes:
- LH (Left Hand) seat
- RH (Right Hand) seat
- BOTH seats

The PFSM (Power-Fold Seat Module) receives voltage signals from the seat position switches for 3 possible seat positions:
- NORMAL
- FOLD
- STOW

The power-stow seat motor assemblies rotate the LH (Left Hand) or RH (Right Hand) seat cushion assemblies together or separately (based on seat[s] selected). The motor assemblies contain Hall-effect sensors that indicate seat position to the PFSM (Power-Fold Seat Module). The power-stow seat motor assemblies are part of the third row seat pivot tube assembly and are not serviceable separately.

The power-fold motor assemblies rotate the LH (Left Hand) or RH (Right Hand) seat backrests. The motor assemblies contain Hall-effect sensors that indicate seat backrest position to the PFSM (Power-Fold Seat Module). The LH (Left Hand) and RH (Right Hand) power-fold motor assemblies are serviceable individually.

The LH (Left Hand) and RH (Right Hand) latch motors receive voltage from the PFSM (Power-Fold Seat Module). The motors share a common ground supplied by the PFSM (Power-Fold Seat Module). The seat latch motors energize and release the seat latch mechanism(s) when the STOW position is selected.

The latch switches are normally open and receive approximately 12 volts from the PFSM (Power-Fold Seat Module). The LH (Left Hand) and RH (Right Hand) latch switches share a common return circuit in series to the PFSM (Power-Fold Seat Module). The PFSM (Power-Fold Seat Module) monitors the latch switch circuits to determine if the seat latches are open or closed. The latch switch is not serviceable separately, a new power seat latch must be installed.

When STOW or FOLD is selected, the backrest folds forward enough to release the spring loaded headrest. If the head restraint is not folded prior to achieving FOLD or STOW positions, the head restraint becomes an obstruction and prevents the seat from completing the seat movement. When an obstruction is detected during any seat movement, the seat stops, reverses a few inches and then stops again until the obstruction is removed. When the obstruction has been removed the seat control switch must be depressed again to reset the request. The seat goes to the home position (seat folded and latched to the floor) and then continues with the requested seat position. After the seat is repaired or a new system component has been installed, the PFSM (Power-Fold Seat Module) also needs to find the seat's 'home' position before completing a selected seat position.