Power Seat Inoperative (W/Memory)

POWER SEAT INOPERATIVE (W/MEMORY-A45)

DIAGNOSTIC FAULT INFORMATION

Diagnostic Fault Information:

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

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.

CIRCUIT/SYSTEM VERIFICATION
1. Ignition ON, observe the scan tool Memory Seat Module seat switch parameters. Verify that none of the seat switch parameters are Active while the switch is in an inactive state.
- If any of the switch parameters are Active, perform the Switch Circuit Test. Component Tests and General Diagnostics
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 any of the switch parameters are not Active, perform the Switch Circuit Test. Component Tests and General Diagnostics
3. If all switch inputs to the MSM function normal, preform the 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. 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.

Motor control circuit test
1. Disconnect the (C3) 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 (C3) harness connector at the memory seat module.
4. Disconnect the (C1) harness connector at the appropriate seat adjuster motor assembly or seat recline motor.
5. Connect a test lamp between the motor control circuit terminals of the inoperative motor.
6. Verify that a test lamp illuminates while pressing the seat switch in both directions.
- If the test lamp does not illuminate for both directions, test the motor 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 after completing the diagnostic procedure. Verification Tests
- Seat Switch Replacement - Power
- Front Seat Adjuster Replacement
- Power Recliner Motor Replacement - Front Seat
- Control Module References for memory seat module replacement, setup, and programming Programming and Relearning