Power Seat Systems — 1996 Jeep Grand Cherokee ZJ Service Manual
Pages 456–462 · 7 pages · 4 words repaired
potentiometers on each of the driver’s power seat motors. The MSM receives messages on the CCD data bus from the Driver Door Module (DDM) (memory set/select switch status), the Powertrain Control Module (PCM) (vehicle speed status), and the Body Control Module (seat belt switch status). The programming in the MSM allows it to process the information from these inputs and send control outputs to each of the driver’s power seat motors. The MSM will prevent the seat memory function from being initiated if the driver’s seat belt is buckled, or if the vehicle is moving.
For diagnosis of the MSM or the CCD data bus, refer to the proper Body Diagnostic Procedures Manual. The MSM cannot be repaired and, if faulty, it must be replaced.
POWER SEAT SWITCH
The power seat can be adjusted in eight different ways using the power seat switch. The switch is located at the lower outboard side of the seat cushion on the seat cushion side shield.
Refer to the owner’s manual for more information on the power seat switch functions and the seat adjusting procedures. The individual switches cannot be repaired. If one switch fails, the entire switch module must be replaced.
POWER LUMBAR SWITCH
The power lumbar adjuster on each front seat can be moved in or out electrically by operating the single two-way switch mounted near the front of the outboard seat cushion side shield. The power lumbar switches cannot be repaired and, if faulty, must be replaced.
POWER SEAT ADJUSTER/MOTORS
There are three reversible motors that operate the power seat adjuster. The motors are connected to worm-drive gearboxes that move the seat adjuster through a combination of screw-type drive units.
The front and rear of a seat are operated by different motors. They can be raised or lowered independently of each other. When the seat switch is pushed to the Up or Down position, both the front and rear motors operate in unison, moving the entire seat up or down. The forward-rearward motor is operated by pushing the seat switch to the Forward or Rearward position.
When a switch is actuated, a battery feed and a ground path are applied through the switch contacts to the motor(s). The motor(s) operate to move the seat in the selected direction until the switch is released, or until the travel limit of the power seat adjuster is reached. When the switch is moved in the opposite direction, the battery feed and ground paths to the motor(s) are reversed through the switch contacts. This causes the motor to run in the opposite direction.
Each motor contains a self-resetting circuit breaker to protect it from overload. Consecutive or frequent resetting of the circuit breakers must not be allowed to continue, or the motors may be damaged. Make the necessary repairs. The motors used on models with the optional memory system also have a position potentiometer included in the motor assembly.
The power seat adjuster and motors cannot be repaired, and are serviced only as a complete unit. If any component in this unit should fail, the entire assembly must be replaced.
POWER RECLINER ADJUSTER/MOTORS
The power recliner adjuster uses a reversible motor to operate the seat back recliner adjuster. The motor is connected to a gearbox that moves the recliner adjuster through a screw-type drive unit.
When the power recliner switch is actuated, a battery feed and a ground path are applied through the switch contacts to the motor. The motor operates to move the seat back in the selected direction until the switch is released, or until the travel limit of the power recliner adjuster is reached. When the switch is moved in the opposite direction, the battery feed and ground paths to the motor are reversed through the switch contacts. This causes the motor to run in the opposite direction.
The motor contains a self-resetting circuit breaker to protect it from overload. Consecutive or frequent resetting of the circuit breaker must not be allowed to continue, or the motor may be damaged. Make the necessary repairs. The motors used on models with the optional memory system also have a position potentiometer included in the motor assembly.
The power recliner adjuster and motor cannot be repaired, and is serviced only as a complete unit. If any component in this unit should fail, the entire assembly must be replaced.
POWER LUMBAR ADJUSTER/MOTORS
There is a reversible motor that operates the power lumbar adjuster. The motor is connected to a wormdrive gearbox that moves the lumbar adjuster mechanism through a cable and lever-type actuator unit.
When the power lumbar switch is actuated, a battery feed and a ground path are applied through the switch contacts to the motor. The motor operates to move the lumbar adjuster mechanism in the selected direction until the switch is released, or until the travel limit of the lumbar adjuster is reached. When the switch is moved in the opposite direction, the battery feed and ground paths to the motor are reversed through the switch contacts. This causes the motor to run in the opposite direction.
The motor contains a self-resetting circuit breaker to protect it from overload. Consecutive or frequent resetting of the circuit breaker must not be allowed to continue, or the motors may be damaged. Make the necessary repairs. The motors used on models with the optional memory system also have a position potentiometer included in the motor assembly.
The power lumbar adjuster and motor cannot be repaired, and are serviced only as a complete unit with the seat back frame. If any component in this unit should fail, the entire assembly must be replaced.
CIRCUIT BREAKER
An automatic resetting circuit breaker in the junction block is used to protect the power seat system circuit. The circuit breaker can protect the system from a short circuit, or from an overload condition caused by an obstructed or stuck seat adjuster. The circuit breaker cannot be repaired. If faulty, it must be replaced.
DIAGNOSIS AND TESTING
POWER SEAT SYSTEM
For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams. Before any testing is attempted, the battery should be fully-charged and all connections and pins cleaned and tightened to ensure proper continuity and grounds.
With the dome lamp on, apply the switch in the direction of the failure. If the dome lamp dims, the seat adjusters may be jamming. Check under and behind the seat for binding or obstructions. If the dome lamp does not dim, proceed with the following component tests.
CIRCUIT BREAKER
For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams. (1) Locate the correct circuit breaker in the junction block. Pull out the circuit breaker slightly, but be sure that the terminals still contact the terminals in the junction block.
(2) Connect the negative lead of a 12-volt DC voltmeter to a good ground.
(3) With the voltmeter positive lead, check both terminals of the circuit breaker for battery voltage.
If only one terminal has battery voltage, the circuit breaker is faulty and must be replaced. If neither terminal has battery voltage, repair the open circuit from the power distribution center as required.
POWER SEAT SWITCH
For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams. To check the power seat switch:
(1) Remove the power seat switch as described in this group.
(2) Use an ohmmeter to test the continuity of the switches in each position. See the Power Seat Switch Continuity chart (Fig. 1). If OK, see the affected Power Adjuster/Motors diagnosis. If not OK, replace the faulty switch module.
POWER LUMBAR SWITCH
For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams. To check the power lumbar switch:
(1) Remove the power lumbar switch as described in this group.
(2) Use an ohmmeter to test the continuity of the switch in each position. See the Power Lumbar Switch Continuity chart (Fig. 2). If OK, see the affected Power Lumbar Adjuster/Motor diagnosis. If not OK, replace the faulty switch.
POWER SEAT ADJUSTER/MOTORS
The tests below apply to a power seat system without the memory system option. For testing of the power seats with the memory system, refer to the proper Body Diagnostic Procedures Manual. For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams.
Operate the power seat switch to move all three seat motors. The seat should move in all directions. If one or more of the motors operate, see the diagnosis for the Power Seat Switch in this group. If no motors operate, proceed as follows:
(1) Check the circuit breaker in the junction block. If OK, go to Step 2. If not OK, replace the faulty circuit breaker.
(2) Remove the power seat switch as described in this group, and check for battery voltage at the fused B(+) circuit cavity of the switch connector. If OK, go to Step 3. If not OK, repair the open circuit to the junction block as required.
(3) Check for continuity between the ground circuit cavity of the switch connector and a good ground. There should be continuity. If OK, go to Step 4. If not OK, repair the open circuit to ground as required.
(4) Test the power seat switch as described in this group. If the switch tests OK, check the circuits for the inoperative motor between the switch and the motor for shorts or opens. If the circuits check OK, replace the faulty power seat adjuster and motors assembly.
POWER RECLINER ADJUSTER/MOTOR
The tests below apply to a power seat system without the memory system option. For testing of the power seats with the memory system, refer to the proper Body Diagnostic Procedures Manual. For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams.
Operate the power seat switch to move the power recliner. The recliner should move in both directions. If the power recliner fails to operate in only one direction, see the diagnosis for the Power Seat Switch in this group. If the power recliner fails to operate at all, proceed as follows:
(1) Check the circuit breaker in the junction block. If OK, go to Step 2. If not OK, replace the faulty circuit breaker.
(2) Remove the power seat switch as described in this group, and check for battery voltage at the fused B(+) circuit cavity of the switch connector. If OK, go to Step 3. If not OK, repair the open circuit to the junction block as required.
(3) Check for continuity between the ground circuit cavity of the switch connector and a good ground. There should be continuity. If OK, go to Step 4. If not OK, repair the open circuit to ground as required.
(4) Test the power seat switch as described in this group. If the switch tests OK, check the circuits for the power recliner between the switch and the motor for shorts or opens. If the circuits check OK, replace the faulty power recliner adjuster and motor assembly.
POWER LUMBAR ADJUSTER/MOTOR
The tests below apply to a power seat system without the memory system option. For testing of the power seats with the memory system, refer to the proper Body Diagnostic Procedures Manual. For circuit descriptions and diagrams, refer to 8W-63 - Power Seat in Group 8W - Wiring Diagrams.
Operate the power lumbar switch to move the power lumbar adjuster. The lumbar adjuster should move in both directions. If the power lumbar adjuster fails to operate in only one direction, see the diagnosis for the Power Lumbar Switch in this group. If the power lumbar adjuster fails to operate at all, proceed as follows:
(1) Check the circuit breaker in the junction block. If OK, go to Step 2. If not OK, replace the faulty circuit breaker.
(2) Remove the power lumbar switch as described in this group, and check for battery voltage at the fused B(+) circuit cavity of the switch connector. If OK, go to Step 3. If not OK, repair the open circuit to the junction block as required.
(3) Check for continuity between the ground circuit cavity of the switch connector and a good ground. There should be continuity. If OK, go to Step 4. If not OK, repair the open circuit to ground as required.
(4) Test the power lumbar switch as described in this group. If the switch tests OK, check the circuits for the power lumbar motor between the switch and the motor for shorts or opens. If the circuits check OK, replace the faulty power lumbar adjuster and motor, which are serviced with the seat back frame assembly.
REMOVAL AND INSTALLATION
POWER SEAT SWITCH
(1) Disconnect and isolate the battery negative cable.
(2) Using a trim stick or other suitable wide flatbladed tool, gently pry the power seat and power recliner switch knobs off of the switch stems.
(3) Remove the three screws securing the seat cushion side shield to the seat cushion frame.
(4) Pull the side shield away from the seat cushion far enough to unplug the switch wiring connector.
(5) Remove the two screws securing the switch to the inside of the side shield (Fig. 3).
(6) Remove the switch from the side shield. (7) Reverse the removal procedures to install.
POWER LUMBAR SWITCH
(1) Disconnect and isolate the battery negative cable.
(2) Remove the three screws securing the seat cushion side shield to the seat cushion frame.
(3) Pull the side shield away from the seat cushion far enough to unplug the switch wiring connector.
(4) Remove the two screws securing the switch to the inside of the side shield.
(5) Remove the switch from the side shield. (6) Reverse the removal procedures to install.
POWER SEAT ADJUSTER/MOTORS
(1) Move the seat to the forward-most position, if possible.
(2) On the driver’s side only, unplug the seat belt switch wire harness from the inboard seat belt.
(3) Remove the single screw securing each of the two rear seat track covers to the rear of the seat tracks and remove the covers.
(4) Remove the single screw securing the rear of each of the two seat tracks to the floor pan.
(5) Move the seat to the rearward-most position, if possible.
(6) Disconnect and isolate the battery negative cable.
(7) Remove the single screw securing the front of each of the two seat tracks to the floor pan (Fig. 4).
(8) Tilt the seat rearward and unplug the power seat wire harness connector located under the seat.
(9) Remove the seat assembly from the vehicle. (10) Remove the three screws securing the outboard seat cushion side shield to the seat cushion frame and pull the shield away from the seat cushion.
(11) Remove the four nuts securing the upper seat adjuster mounting rails to the seat cushion frame.
(12) Unplug the wire harness connectors as required, depending upon how the vehicle is equipped, to separate the power seat motors and adjuster from the seat cushion frame.
(13) Reverse the removal procedures to install. Tighten the seat mounting hardware as follows:
• Seat cushion frame to adjuster nuts - 20 N·m (15 ft. lbs.)
• Seat adjuster to floor pan bolts - 29 N·m (20 ft. lbs.).
POWER RECLINER ADJUSTER/MOTOR
(1) Move the power seat adjuster to its upper-most and forward-most stop positions.
(2) Remove the three screws securing the outboard seat cushion side shield to the seat cushion frame and pull the shield away from the seat so that the power recliner adjuster lower bracket can be seen.
(3) If possible, adjust the seat back with the power recliner switch so that both of the two bolts in the power recliner adjuster lower bracket can be accessed.
(4) Disconnect and isolate the battery negative cable.
(5) Remove the two bolts securing the power recliner adjuster lower bracket to the seat cushion frame (Fig. 5).
(6) Remove the inboard seat back pivot bolt. (7) Unplug the wiring connectors, depending upon how the vehicle is equipped, as required to remove the seat back from the seat cushion.
(8) Remove the seat back cover far enough to access the two bolts securing the power recliner adjuster upper bracket to the seat back frame (Fig. 6). Refer to Group 23 - Body components for the seat back cover removal procedures.
(9) Remove the power recliner adjuster and motor unit from the seat back frame.
(10) Reverse the removal procedures to install. Tighten the hardware as follows:
• Inboard pivot bolt - 40 N·m (29 ft. lbs.) • Recliner bracket bolts - 28 N·m (20 ft. lbs.).
POWER LUMBAR ADJUSTER/MOTOR
(1) Remove the power recliner adjuster and motor from the seat back frame as described in this group.
(2) Remove all of the seat back trim from the seat back. Refer to Group 23 - Body Components for the procedures.
(3) Replace the seat back frame assembly with the lumbar adjuster and motor (Fig. 7).
(4) Reverse the removal procedures to install.
MEMORY SEAT MODULE
(1) Move the seat to the upper-most and forwardmost position, if possible.
(2) Unplug the seat belt switch wire harness from the inboard seat belt.
(3) Remove the single screw securing each of the two rear seat track covers to the rear of the seat tracks and remove the covers.
(4) Remove the single screw securing the rear of each of the two seat tracks to the floor pan.
(5) Move the seat to the rearward-most position, if possible.
(6) Remove the single screw securing the front of each of the two seat tracks to the floor pan.
(7) Disconnect and isolate the battery negative cable.
(8) Carefully tilt the seat back towards the outboard side of the vehicle.
(9) Remove the two wire harness retainers out of the seat adjuster top rail (Fig. 8).
(10) Slide the memory seat module off of the mounting bracket slide tabs far enough to unplug the wire harness connectors.
(11) Remove the module from under the seat cushion.
(12) Reverse the removal procedures to install. (13) Following the installation it will be necessary to initialize the memory seat module. This is done by moving each of the power seat adjuster motors
(including the power recliner and power lumbar motors) through its full range of motion using the power seat switches. It is necessary for the memory seat module to learn the motor sensor values in each of the adjuster hard stop positions, so that the module can function properly.