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Power Seat Inoperative (with Memory-A45)



Power Seat Inoperative (with Memory-A45)

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

A low current battery voltage is supplied at all times to the memory seat module (MSM) from the 7.5A MEMORY RPA 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 PWR SEATS 30A 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 the seat switch parameters are Inactive while the switch is in an inactive state.

• If not the specified value, perform the Seat Adjuster Switch Circuit Test.

2. Observe the scan tool Memory Seat Module seat switch parameters while pressing the related seat switch. The reading should be Active.

• If not the specified value, perform the Seat Adjuster Switch Circuit Test.

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 F 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 F. 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 inoperative seat adjuster motor.
5. Connect a test lamp between the motor control circuits terminal A and terminal B.
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.

Component Testing

1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Test for infinite resistance between each signal terminal (A, B, D, E, and J-M) and the B+ terminal F 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 of resistance between each signal terminal (A, B, D, E, and J-M) and the B+ terminal F with the switch in the closed 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
* Seat Adjuster Motor Replacement - Horizontal
* Seat Adjuster Motor Replacement - Vertical
* Front Seat Recliner Actuator Motor Replacement
* Control Module References for memory seat module replacement, setup, and programming. Programming and Relearning
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