Power Seat Inoperative Without Memory A45
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ Seat Adjuster Switch | 1 | 1 | -- | -- |
Front Vertical Motor Down Control | 1 | 1 | -- | -- |
Front Vertical Motor Up Control | 1 | 1 | -- | -- |
Horizontal Motor Forward Control | 1 | 1 | -- | -- |
Horizontal Motor Rearward Control | 1 | 1 | -- | -- |
Rear Vertical Motor Down Control | 1 | 1 | -- | -- |
Rear Vertical Motor Up Control | 1 | 1 | -- | -- |
Recline Motor Forward Control | 1 | 1 | -- | -- |
Recline Motor Rearward Control | 1 | 1 | -- | -- |
Ground - Seat Adjuster Switch | -- | 1 | -- | -- |
1. Power seat inoperative | ||||
Circuit/System Description
Power seats without memory are completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat adjuster switch from the 25A DRIVER SEAT or PASS SEAT circuit breaker that is located in the left I/P fuse block. When the seat adjuster switches are in an inactive state, the switch contacts are closed to the switch ground circuit.
All seat motors are reversible. For example, when the seat horizontal forward switch is pressed to move the entire seat forward, battery voltage is applied through the switch contacts and the seat horizontal motor forward control circuit to the motor. The motor is grounded through the horizontal motor rearward switch contacts and the horizontal motor rearward control circuit to the motor. The motor runs in order 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 opposite circuits causing the motor to run in the opposite direction. All seat motors are powered this way.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Power Seats System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Operate the switches for the seat directional motors listed below in both directions. The seat should move in the commanded directions.
| • | Horizontal Motor |
| • | Front Vertical Motor |
| • | Rear Vertical Motor |
| • | Recline Motor (+AN3) |
| ⇒ | If just the recline function is inoperative, refer to the Recline Motor Circuit Test. |
| ⇒ | If the power seat is inoperative in all directions, refer to the Seat Adjuster Switch Circuit Test. |
| ⇒ | If 1 or more of the seat adjuster motors operate, refer to the appropriate seat motor test listed below: |
| • | Seat Adjuster Motor Circuit Test (-HP2) |
| • | Seat Adjuster Motor Circuit Test (+HP2) |
Circuit/System Testing
Seat Adjuster Switch Circuit Test
- Ignition OFF, disconnect the harness connector at the seat adjuster switch.
- Test for less than 5 ohms between the ground circuit terminal B and ground.
- Ignition ON, verify that a test lamp illuminates between the appropriate B+ circuit listed below and ground:
- If all circuits test normal, test or replace the seat adjuster switch.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| • | Terminal E (+AN3) |
| • | Terminal D (-AN3, +HP2) |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
Seat Adjuster Motor Circuit Test (+AN3/-HP2)
- Ignition OFF, disconnect the harness connector at the seat adjuster motor assembly.
- Verify that a test lamp illuminates between the appropriate control circuits listed below while pressing the seat switch in both directions.
- If all circuits test normal, test or replace the seat adjuster motor assembly.
| • | Seat horizontal motor terminal 3 and terminal 6 |
| • | Seat front vertical motor terminal 2 and terminal 5 |
| • | Seat rear vertical motor terminal 1 and terminal 4 |
| ⇒ | If the test lamp does not illuminate for both directions, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, test or replace the seat adjuster switch. |
Seat Adjuster Motor Circuit Test (+HP2)
- Disconnect the harness connector at the appropriate seat motor.
- Verify that the test lamp illuminates between control circuit terminal 1 and control circuit terminal 2 while pressing the seat switch in both directions.
- If all circuits test normal, test or replace the seat motor.
| ⇒ | If the test lamp does not illuminate for both directions, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, test or replace the seat adjuster switch. |
Recliner Motor Circuit Test
- Ignition OFF, disconnect the harness connector at the recline motor.
- Verify that the test lamp illuminates between control circuit terminal A and control circuit terminal B while pressing the recline switch in both directions.
- If all circuits test normal, test or replace the recline motor.
| ⇒ | If the test lamp does not illuminate for both directions, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, test or replace the seat adjuster switch. |
Component Testing
Seat Adjuster Switch Test
- Ignition OFF, disconnect the harness connector at the seat adjuster switch.
- Test for infinite resistance between each control terminal and the B+ terminal with the switch in the open position.
- Test for less than 1 ohm between each control terminal and the B+ terminal with the switch in the closed position.
- Test for less than 1 ohm between each control terminal and the ground terminal with the switch in the open position.
| ⇒ | If less than the specified value, replace the seat adjuster switch. |
| ⇒ | If greater than the specified range, replace the seat adjuster switch. |
| ⇒ | If greater than the specified range, replace the seat adjuster switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Power Seat Inoperative With Memory A45
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
B+ MSM Terminal 5 X3 | 1 | 1 | 1 | -- | -- |
B+ MSM Terminal 6 X3 | 2 | 2 | 2 | -- | -- |
B+ Seat Adjuster Switch | 2 | 1 | 1 | -- | -- |
Front Vertical Up Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Front Vertical Down Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Horizontal Forward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Horizontal Rearward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Rear Vertical Up Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Rear Vertical Down Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Recline Forward Switch Signal | 2 | 1 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Recline Rearward Switch Signal | 2 | 1 | -- | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Driver Seat Front Vertical Motor Down Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A |
Driver Seat Front Vertical Motor Up Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A |
Driver Seat Horizontal Motor Forward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A |
Driver Seat Horizontal Motor Rearward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A |
Driver Seat Rear Vertical Motor Down Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A |
Driver Seat Rear Vertical Motor Up Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A |
Driver Seat Recline Motor Forward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A |
Driver Seat Recline Motor Rearward Control | B3920 02 | B1335 00, B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A |
Ground - MSM Terminal 1 X3 | -- | -- | -- | -- | -- |
Ground - MSM Terminal 4 X3 | -- | -- | -- | -- | -- |
Ground - Inline X303 Terminal B8 | -- | 2 | 2 | -- | -- |
1. Power seat and memory functions inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device | |||||
Circuit/System Description
Battery positive voltage is supplied at all times to the memory seat module (MSM) through the DSM 10A fuse located in the I/P fuse block. 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 through the DRIVER 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, lumbar, or adjustable pedal 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
Connector End View Reference
Description and Operation
Memory Seats Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the scan tool Driver Position Module seat switch parameters while pressing the appropriate seat switch. The reading should change between Inactive and Active.
- If all seat switch inputs to the MSM function normal, refer to the appropriate test listed below:
| ⇒ | If the reading does not change between the specified values, refer to the Seat Adjuster Switch Circuit Test. |
| • | Seat Motor Control Circuit Test |
| • | Recline Motor Control Circuit Test |
Circuit/System Testing
Seat Adjuster Switch Circuit Test
- Ignition OFF, disconnect the harness connector at the seat adjuster switch.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal E and ground.
- Install a 3A fused jumper wire between the appropriate signal circuit listed below and the B+ circuit terminal E. Verify the scan tool seat switch parameter is Active.
- If all circuits test normal, test or replace the seat adjuster switch.
| ⇒ | 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 MSM. |
| • | Front vertical upward switch terminal A |
| • | Front vertical downward switch terminal K |
| • | Rear vertical upward switch terminal F |
| • | Rear vertical downward switch terminal J |
| • | Horizontal forward switch terminal D |
| • | Horizontal rearward switch terminal C |
| • | Recline forward switch terminal H |
| • | Recline rearward switch terminal G |
| ⇒ | If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM. |
Seat Motor Control Circuit Test
- Ignition OFF, disconnect the X3 harness connector at the MSM.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.
- Ignition OFF, connect the X3 harness connector at the MSM and disconnect the X1 harness connector at the seat adjuster motor assembly.
- Connect a test lamp between the appropriate control circuits listed below:
- 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 all circuits test normal, test or replace the seat motor.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| • | Seat horizontal motor terminal 3 and terminal 6 |
| • | Seat front vertical motor terminal 2 and terminal 5 |
| • | Seat rear vertical motor terminal 1 and terminal 4 |
| ⇒ | 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. |
Recline Motor Control Circuit Test
- Ignition OFF, disconnect the harness connector at the recline motor.
- Connect a test lamp between control circuit terminal A and control circuit terminal B.
- Ignition ON, command the Recline Forward/Rearward with a scan tool. The test lamp should turn ON when commanding the forward and rearward states.
- If all circuits test normal, test or replace the recline motor.
| ⇒ | 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. |
Component Testing
- Ignition OFF, disconnect the harness connector at the seat adjuster switch.
- Test for infinite resistance between each seat direction signal terminal listed below and the B+ terminal E with the switch in the open position.
- 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 upward switch terminal A |
| • | Front vertical downward switch terminal K |
| • | Rear vertical upward switch terminal F |
| • | Rear vertical downward switch terminal J |
| • | Horizontal forward switch terminal D |
| • | Horizontal rearward switch terminal C |
| • | Recline forward switch terminal H |
| • | Recline rearward switch terminal G |
| ⇒ | If not the specified value, replace the seat adjuster switch. |
| • | Front vertical upward switch terminal A |
| • | Front vertical downward switch terminal K |
| • | Rear vertical upward switch terminal F |
| • | Rear vertical downward switch terminal J |
| • | Horizontal forward switch terminal D |
| • | Horizontal rearward switch terminal C |
| • | Recline forward switch terminal H |
| • | Recline rearward switch terminal G |
| ⇒ | If greater than the specified range, replace the adjuster switch switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for MSM replacement, setup, and programming |
