Power Seat Inoperative (With Memory A45)
Power Seat Inoperative (with Memory A45)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
A low current battery voltage is supplied at all times to the memory seat module (MSM) from the 10A MSM LOGIC fuse. This voltage is used by the MSM for logic power and to supply battery reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the MSM/LT FRT PWR SEAT 25A circuit breaker. This voltage is connected to a power rail internal to the MSM and is used to drive the power seat motors, lumbar motors, and seat heater elements on vehicles equipped with heated seats. Each seat and lumbar adjuster motor is controlled by the MSM through 2 motor control circuits. The MSM connects all motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The MSM checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat or lumbar motors.
All motors are reversible. For example, when the seat switch is operated to move the entire seat forward, battery positive voltage is applied through the switch contacts and the power seat horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery voltage through the driver seat horizontal motor forward control circuit and ground through the driver seat horizontal motor rearward control circuit to the motor. The motor runs to drive the entire seat forward until the switch is released. Moving the entire seat rearward works similarly to moving the entire 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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for Scan Tool Information
Circuit/System Verification
1. Ignition ON, observe the scan tool Memory Seat Module seat switch parameters. All of the seat switch parameters should be Inactive.
• If not the specified value, refer to the Seat Adjuster Switch Test.
2. Observe the scan tool Memory Seat Module seat switch parameters while pressing and releasing the related seat switch. The reading should change between Inactive and Active.
• If not the specified value, refer to the Seat Adjuster Switch Test.
3. If all switch inputs to the MSM function normal, refer to the Seat Adjuster Motor Test.
Circuit/System Testing
Seat Adjuster Switch 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. If the circuit tests normal, replace the memory seat module.
3. Install a 3A fused jumper wire between the inoperative switch signal circuit terminal and the B+ circuit terminal E. Verify the related scan tool seat switch parameter is Active.
• If not Active, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
4. If all circuits test normal, test or replace the seat adjuster switch.
Seat Adjuster Motor Test
1. Disconnect the X3 harness connector at the memory seat module.
2. Verify that a test lamp illuminates between the B+ circuit terminal 5 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 X3 harness connector at the memory seat module.
4. Disconnect the X1 harness connector at the inoperative seat adjuster motor.
5. Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
6. Command the appropriate seat motor Forward/Up and Rearward/Down with a scan tool. The test lamp should turn ON when commanding the Forward/Up and Rearward/Down states. .
• If the test lamp remains OFF during either of the commands, test the control circuits for an open/high resistance. If the circuits test normal replace the MSM.
7. If all circuits test normal, test or replace the inoperative seat motor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Seat Recliner Actuator Motor Replacement (Front Seat Recliner Actuator Motor Replacement)
* Control Module References (Programming and Relearning) for memory seat module replacement, setup, and programming