Power Seat Inoperative (w/Memory)
Power Seat Inoperative (w/Memory)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The 8-way power driver seat with memory is controlled by the memory seat module (MSM). The low current battery supply circuit from the DSM 10A fuse supplies the logic power and reference voltages to the MSM. The high current battery supply circuit from the DRIVER SEAT 2 25A circuit breaker supplies the MSM power rail 1 which is used to drive the power seat motors, adjustable pedals motor, and seat heater elements with heated seats only. The MSM supplies a battery voltage reference circuit to the seat adjuster and lumbar switches. The switch signal circuits are referenced from ground within the MSM and when a switch is activated the signal circuit goes high. Each seat adjuster motor is controlled by the MSM through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the MSM. The MSM operates the seat adjuster motors by switching one of a motors control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.
Circuit/System Verification
1. Install a scan tool and display the MSM switch inputs.
2. Verify that none of the power seat switch parameters are Active while in an inactive state.
^ If not the specified value, refer to the Power Seat Switch Circuit Test.
3. Verify that the power seat switch parameters are Active while the switch is pressed.
^ If not the specified value, refer to the Power Seat Switch Circuit Test.
4. Verify that none of the lumbar switch parameters are Active while in an inactive state.
^ If not the specified value, refer to the Lumbar Switch Circuit Test.
5. Verify that the lumbar switch parameters are Active while the switch is pressed.
^ If not the specified value, refer to the Lumbar Switch Circuit Test.
6. If the switch inputs to the MSM function normal, refer to the affected Motor Control Circuit Test.
Circuit/System Testing
Power Seat Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the power seat switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal E and ground.
^ If the test lamp does not illuminate, test the B+ reference circuit for a short to ground or an open/high resistance.
3. Verify the scan tool power seat switch parameters are Inactive.
^ If not the specified values, test the affected signal circuit terminal listed for a short to voltage. If the circuit tests normal, replace the MSM.
* Front vertical down switch terminal K
* Front vertical up switch terminal A
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Rear vertical down switch terminal J
* Rear vertical up switch terminal F
* Recline forward switch terminal H
* Recline rearward switch terminal G
4. Install a 3A fused jumper wire between the affected signal circuit terminal listed and the B+ reference circuit terminal E. Verify the affected scan tool power seat switch parameter is Active.
* Front vertical down switch terminal K
* Front vertical up switch terminal A
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Rear vertical down switch terminal J
* Rear vertical up switch terminal F
* Recline forward switch terminal H
* Recline rearward switch terminal G
^ If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the power seat switch.
Lumbar Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal G and ground.
^ If the test lamp does not illuminate, test the B+ reference circuit for a short to ground or an open/high resistance.
3. Verify the scan tool lumbar switch parameters are Inactive.
^ If not the specified values, test the affected signal circuit terminal listed for a short to voltage. If the circuit tests normal, replace the MSM.
* Lumbar down switch terminal K
* Lumbar up switch terminal A
* Lumbar forward switch terminal D
* Lumbar rearward switch terminal C
4. Install a 3A fused jumper wire between the affected signal circuit terminal listed and the B+ reference circuit terminal G. Verify the affected scan tool lumbar switch parameter is Active.
* Lumbar down switch terminal K
* Lumbar up switch terminal A
* Lumbar forward switch terminal D
* Lumbar rearward switch terminal C
^ If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the lumbar switch.
Seat Adjuster Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the seat adjuster assembly.
2. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed and ground.
* Rear vertical terminal 1
* Front vertical terminal 2
* Horizontal terminal 3
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
3. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed and ground.
* Rear vertical terminal 4
* Front vertical terminal 5
* Horizontal terminal 6
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
4. Connect a test lamp between the affected control circuit terminals listed.
* Rear vertical terminal 1 to terminal 4
* Front vertical terminal 2 to terminal 5
* Horizontal terminal 3 to terminal 6
5. Command the affected function in both directions with a scan tool. The test lamp should turn ON when commanding the affected function in both states.
^ If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the MSM.
6. If all circuits test normal, test or replace the seat adjuster.
Recline Motor Control Circuit Test
1. Ignition OFF, disconnect the harness connector at the recline motor.
2. Ignition OFF, test for less than 1.0 ohm between the control circuit terminal A and ground.
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
3. Ignition OFF, test for less than 1.0 ohm between the control circuit terminal B and ground.
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.
4. Connect a test lamp between control circuit terminal A and control circuit terminal B.
5. Command the recline Forward and Rearward with a scan tool. The test lamp should turn ON when commanding the Forward and Rearward states.
^ If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the MSM.
6. If all circuits test normal, test or replace the recliner motor.
Lumbar Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the lumbar adjuster assembly.
2. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed and ground.
* Vertical lumbar terminal A
* Horizontal lumbar terminal C
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the MSM.
3. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed and ground.
* Vertical lumbar terminal B
* Horizontal lumbar terminal D
^ If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the MSM.
4. Connect a test lamp between affected control circuit terminals listed.
* Vertical lumbar terminal A to terminal B
* Horizontal lumbar terminal C to terminal D
5. Command the affected function in both directions with a scan tool. The test lamp should turn ON when commanding the affected function in both states.
^ If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the MSM.
6. If all circuits test normal, test or replace the lumbar support.
Component Testing
Seat Adjuster Switch Test
1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Test for infinite resistance between each control terminal and the B+ terminal with the switch in the open position.
^ If less than the specified value, replace the seat adjuster switch.
3. Test for less than 1 ohm between each control terminal and the B+ terminal with the switch in the closed position.
^ If greater than the specified range, replace the seat adjuster switch.
4. Test for less than 1 ohm between each control terminal and the ground terminal with the switch in the open position.
^ If greater than the specified range, replace the seat adjuster switch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Power Seat Switch Replacement
* Lumbar Switch Replacement
* Front Seat Adjuster Replacement (Power)
* Front Seat Lumbar Support Replacement
* Front Seat Recliner Actuator Motor Replacement