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 provide 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 Front Down Control | 1 | 1 | -- | -- |
Front Vertical Motor Front UP Control | 1 | 1 | -- | -- |
Horizontal Motor Forward Control | 1 | 1 | -- | -- |
Horizontal Motor Rearward Control | 1 | 1 | -- | -- |
Rear Vertical Motor Rear Down Control | 1 | 1 | -- | -- |
Rear Vertical Motor Rear 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 seat without memory is completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the driver seat adjuster switch from the LF/FRT/PWR/SEAT circuit breaker and the passenger seat adjuster switch from the RT/FRT/PWR/SEAT circuit breaker that are located in the rear 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
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 |
| ⇒ | 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 Seat Adjuster Motor Circuit Test. |
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 B+ circuit terminal E 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. |
| ⇒ | 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
- Ignition OFF, disconnect the harness connector at the appropriate seat adjuster motor.
- Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
- Verify that the test lamp illuminates while pressing the appropriate seat switch in both directions.
- If all circuits test normal, replace the seat adjuster 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 replace the seat adjuster switch. |
Component Testing
Seat Adjuster Switch
- Ignition OFF, disconnect the harness connector at the seat adjuster switch.
- Test for infinite resistance between each control terminal listed below and the B+ terminal E with the switch in the open position.
- Test for less than 1 ohm between each control terminal listed below and the B+ terminal E with the switch in the closed position.
- Test for less than 1 ohm between each control terminal listed below and the ground terminal B with the switch in the open 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. |
| • | 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 seat adjuster switch. |
Seat Motor
- Ignition OFF, disconnect the harness connector at the appropriate seat motor.
- Install a 30A fused jumper wire between the control terminal 1 and 12 volts. Momentarily install a jumper wire between the control terminal 5 and ground. The seat motor should momentarily perform the appropriate FORWARD/REARWARD/UP/DOWN function.
- Reverse the polarity of jumper wires; the a seat motor should perform in the opposite direction.
Important: When performing the following tests, make sure that the seat is not already in the position the test is attempting to produce.
| ⇒ | If the function does not perform as specified, replace the seat motor. |
| ⇒ | If the function does not perform as specified, replace the seat motor. |
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, B2425 0D, B2430 0D | 1, B2425 0D, B2430 0D | 1, B2425 0D, B2430 0D | -- | -- |
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 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A |
Driver Seat Front Vertical Motor Up Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2355 5A |
Driver Seat Horizontal Motor Forward Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A |
Driver Seat Horizontal Motor Rearward Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2375 5A |
Driver Seat Rear Vertical Motor Down Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A |
Driver Seat Rear Vertical Motor Up Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B2365 5A |
Driver Seat Recline Motor Forward Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A |
Driver Seat Recline Motor Rearward Control | B3920 02 | B1335 0B | 1 | B3920 01 | B1335 42, B1335 4B, B1825 5A |
Ground - Terminal 1 X3 | -- | -- | -- | -- | -- |
Ground - Terminal 4 X3 | -- | -- | -- | -- | -- |
Ground - Inline X300 Terminal 14 | -- | 2 | 2 | -- | -- |
1. Power seat and memory functions inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device | |||||
Circuit/System Description
Battery voltage is supplied at all times to the memory seat module (MSM) from the 10A MSM fuse. This voltage is used by the MSM for logic power and to supply reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the LF/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 motor, 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
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 Memory Seat Module seat switch parameters while pressing the appropriate seat switch. The reading should change between Inactive and Active.
- If all switch inputs to the MSM function normal, refer to the Seat Adjuster Motor Circuit Test.
| ⇒ | If the reading does not change between the specified values, refer to the Seat Adjuster Switch 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 appropriate 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 Adjuster Motor 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 memory seat module and disconnect the X1 harness connector at the appropriate seat adjuster motor.
- Connect a test lamp between control circuit terminal 1 and control circuit terminal 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 all circuits test normal, test or replace the seat adjuster motor.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | 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
Seat Adjuster Switch
- 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. |
Seat Motor
- Ignition OFF, disconnect the harness connector at the appropriate seat motor.
- Install a 30A fused jumper wire between the control terminal 1 and 12 volts. Momentarily install a jumper wire between the control terminal 5 and ground. The seat motor should momentarily perform the appropriate FORWARD/REARWARD/UP/DOWN function.
- Reverse the polarity of jumper wires; the a seat motor should perform in the opposite direction.
Important: When performing the following tests, make sure that the seat is not already in the position the test is attempting to produce.
| ⇒ | If the function does not perform as specified, replace the seat motor. |
| ⇒ | If the function does not perform as specified, replace the seat motor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for MSM replacement, setup, and programming |
