Power Seat Inoperative w/o Memory

Power seats without memory are completely controlled through the power seat switch. Battery voltage is supplied to the power seat switch through the power seat circuit breaker. While the seat adjuster switches are in an inactive state the switch contacts are closed to the power seat switch ground circuit. When a power seat switch is pressed to an active state the switch contact is closed to the battery voltage supply circuit. Each seat adjuster motor is controlled by the power seat switch through 2 motor control circuits. 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.

Schematic Reference

Connector End View Reference

Power Seat Component Views

Electrical Information Reference

1. Disconnect the seat adjuster or power lumbar switch connector.
2. Verify that a test lamp illuminates when connected from battery voltage to the ground circuit terminal.

⇒	If the test lamp does not illuminate, repair the ground circuit for an open/high resistance.

3. Verify that a test lamp illuminates when connected from the battery supply circuit terminal to ground.

⇒	If the test lamp does not illuminate, repair the battery supply circuit for an open/high resistance or short to ground.

4. Connect the seat adjuster or power lumbar switch connector and disconnect the inoperative motor assembly connector.
5. Connect a test lamp across the inoperative motor control circuit terminals.
6. Verify that the test lamp illuminates when the appropriate switch is pressed.

⇒	If the test lamp does not illuminate, repair the motor circuits for an open/high resistance or short to ground. If the circuits test normal replace the seat adjuster or power lumbar switch.

7. If the circuits test normal, replace the inoperative motor assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Power Seat Inoperative w/Memory

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.

Schematic Reference

Driver Seat Schematics

Connector End View Reference

Power Seat Connector End Views

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

1. Install a scan tool and display the MSM switch inputs.
2. Verify that none of the switches are displayed as Active while in an inactive state.

⇒	If any of the switch inputs are Active, perform the affected Switch Circuit Test.

3. Verify that the switch inputs are displayed as Active while the switch is pressed.

⇒	If any of the switch inputs remain Inactive while the switch is pressed, perform the affected Switch Circuit Test.

4. If the switch inputs to the MSM function normal, perform the Motor Control Circuit Test.

Seat Adjuster Switch Circuit Test

1. Disconnect the MSM connector C7 and verify that none of the adjuster switch inputs are displayed as Active.

⇒	If any of the switch inputs are Active, replace the MSM.

2. Verify that battery voltage is not present at the affected switch signal circuit terminal while the switch is inactive.

⇒	If battery voltage is present while the switch is not pressed, replace the seat adjuster switch.

3. Verify that battery voltage is present at the affected switch signal circuit terminal while pressing the switch.

⇒	If battery voltage is not present while the switch is pressed, repair the switch supply circuit for an open/high resistance. If the circuit tests normal replace the seat adjuster switch.

4. If the circuits test normal replace the MSM.

Lumbar Switch Circuit Test

1. Disconnect the MSM connector C6 and verify that none of the lumbar switch inputs are displayed as Active.

⇒	If any of the switch inputs are Active, replace the MSM.

2. Verify that battery voltage is not present at the affected switch signal circuit terminal while the switch is inactive.

⇒	If battery voltage is present while the switch is not pressed, replace the lumbar switch.

3. Verify that battery voltage is present at the affected switch signal circuit terminal while pressing the switch.

⇒	If battery voltage is not present while the switch is pressed, repair the switch supply circuit for an open/high resistance. If the circuit tests normal replace the lumbar switch.

4. If the circuits test normal replace the MSM.

Motor Control Circuit Test

1. Disconnect the MSM connector C3.
2. Verify that a test lamp illuminates when connected from the high current battery supply circuit terminal 5 to ground.

⇒	If the test lamp does not illuminate, repair the high current battery supply circuit for an open or short to ground.

3. Connect the MSM connector C3 and disconnect the seat adjuster assembly or lumbar adjuster assembly connector C2.
4. Connect a test lamp across the affected motor control circuit terminals.
5. Verify that the test lamp illuminates while the affected switch is pressed.

⇒	If the test lamp does not illuminate, repair the motor control circuits for an open/high resistance. If the circuits test normal replace the MSM.

6. If the circuits test normal replace the affected adjuster assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.