Power Seat Inoperative (With Memory A45)
Power Seat Inoperative (With Memory A45)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Battery voltage is supplied at all times to the memory seat module (MSM) from the 10A LGM/DSM fuse located in the rear fuse block. This voltage is used by the MSM for logic power and to supply battery voltage to the seat and lumbar adjuster switches. Battery voltage is supplied at all times to the MSM from the SEATS 30A circuit breaker located in the rear fuse block. This voltage is used by the MSM to drive the driver seat adjuster motors, recline motor and the lumbar motor.
All motors are reversible. For example, when the seat switch is pressed to move the seat forward, battery voltage is applied through the switch contacts and the seat horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery voltage through the seat horizontal motor forward control circuit and ground through the seat horizontal motor rearward control circuit to the motor. The motor runs to drive the seat forward until the switch is released. Moving the seat rearward works similarly to moving the seat forward, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction.
Reference Information
Schematic Reference
Driver Seat Schematics (Driver Seat Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Memory Seats Description and Operation (Memory Seats Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool seat adjuster switch parameters while operating each adjuster switch in both directions. The reading should change between Inactive and the desired direction.
• If any of the switch input parameters are Inactive or Invalid while the switch is pressed, refer to the Seat Adjuster Switch Circuit Test
2. If all seat switch inputs to the MSM function normal, refer to Seat Motor Control Circuit Test.
Circuit/System Testing
Seat Adjuster Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal E and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Verify the scan tool seat switch parameters listed below are Inactive:
* Recline Switch
* Horizontal Position Switch
* Rear Vertical Position Switch
* Front Vertical Position Switch
• If not the specified value, test the appropriate signal circuit listed below for a short to voltage. If the circuit tests normal, replace the MSM.
* Front vertical up switch terminal K
* Front vertical down switch terminal J
* Rear vertical up switch terminal H
* Rear vertical down switch terminal G
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Recline forward switch terminal F
* Recline rearward switch terminal A
4. Install a 3A fused jumper wire between the appropriate signal circuit listed below and the B+ circuit terminal E. Verify the appropriate scan tool seat position switch parameter is Forward/Rearward or Up/Down.
* Front vertical up switch terminal K
* Front vertical down switch terminal J
* Rear vertical up switch terminal H
* Rear vertical down switch terminal G
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Recline forward switch terminal F
* Recline rearward switch terminal A
• If not the specified value, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the seat adjuster switch.
Seat Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the MSM.
2. Verify that a test lamp illuminates between the B+ circuit terminal C and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Connect the X1 harness connector at the MSM and disconnect the harness connector at the appropriate seat motor.
4. Connect a test lamp between control circuit terminal A and control circuit terminal B.
5. Ignition ON, command the appropriate seat motor in the Up/Down or Forward/Rearward directions with a scan tool. The test lamp should turn ON when commanding the up and down or forward and rearward states.
• If the test lamp remains OFF during either of the commands, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal replace the MSM.
6. If all circuits test normal, test or replace the seat motor.
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 seat direction signal terminal listed below and the B+ terminal E with the switch in the open position.
* Front vertical up switch terminal K
* Front vertical down switch terminal J
* Rear vertical up switch terminal H
* Rear vertical down switch terminal G
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Recline forward switch terminal F
* Recline rearward switch terminal A
• If not the specified value, replace the seat adjuster switch.
3. Test for less than 1 ohm between each seat direction signal terminal listed below and the B+ terminal E with the switch in the closed position.
* Front vertical up switch terminal K
* Front vertical down switch terminal J
* Rear vertical up switch terminal H
* Rear vertical down switch terminal G
* Horizontal forward switch terminal D
* Horizontal rearward switch terminal C
* Recline forward switch terminal F
* Recline rearward switch terminal A
• If greater than the specified range, replace the seat adjuster switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Power Seat Switch Replacement (Power Seat Switch Replacement)
* Power Seat Adjuster Mechanism Replacement (Power Seat Adjuster Mechanism Replacement)
* Control Module References (Programming and Relearning) for MSM replacement, programming, and setup.