Power Seat Inoperative w/o 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. |
Circuit/System Description
Power seat without memory is completely controlled through the seat adjuster switch. Battery voltage is supplied at all times to the seat adjuster switch from the memory seat module MSM/RT FRT PWR SEAT 25A circuit breaker that is 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
Power Seat Connector End Views
Electrical Information Reference
Circuit/System Testing
- Disconnect the harness connector at the seat adjuster switch.
- Test for less than 1 ohm of resistance between the ground circuit terminal B and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal and ground.
- Connect the harness connector at the seat adjuster switch.
- Disconnect the harness connector at the appropriate seat motor assembly.
- Connect a test lamp between the motor control circuit terminals for the inoperative motor.
- Verify that the test lamp illuminates while pressing the appropriate seat switch in both directions.
- If the circuits test normal replace the inoperative motor assembly.
| ⇒ | If greater than 1 ohm, 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. |
| ⇒ | If the test lamp does not illuminate for both directions, test the motor circuits for a short to ground or an open/high resistance. If the circuits test normal replace the seat adjuster switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Power Seat Inoperative w/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+ (C3 Terminal 5) | 1 | 1 | -- | -- |
B+ (C3 Terminal 6) | 2 | 2 | -- | -- |
B+ (C3 Terminal 3) | 2 | 1 | -- | -- |
Front Vertical Up Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Front Vertical Down Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Rear Vertical Up Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Rear Vertical Down Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Horizontal Forward Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Horizontal Rearward Switch Signal | 2 | 1 | B1735 01, B1740 01, B1745 01, B1750 01, B1755 01, B1760 01, B1815 01, B1820 01 | -- |
Recline Forward Switch Signal | 2 | 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 | 1 | B3920 01 | B2355 5A |
Driver Seat Front Vertical Motor Up Control | B3920 02 | 1 | B3920 01 | B2355 5A |
Driver Seat Rear Vertical Motor Down Control | B3920 02 | 1 | B3920 01 | B2365 5A |
Driver Seat Rear Vertical Motor Up Control | B3920 02 | 1 | B3920 01 | B2365 5A |
Driver Seat Horizontal Motor Forward Control | B3920 02 | 1 | B3920 01 | B2375 5A |
Driver Seat Horizontal Motor Rearward Control | B3920 02 | 1 | B3920 01 | B2375 5A |
Driver Seat Recline Motor Forward Control | B3920 02 | 1 | B3920 01 | B1825 5A |
Driver Seat Recline Motor Rearward Control | B3920 02 | 1 | B3920 01 | B1825 5A |
Ground (C3 Terminal 1) | -- | -- | -- | -- |
Ground (C3 Terminal 1) | -- | -- | -- | -- |
Ground (Inline C315 Terminal 3) | -- | 2 | -- | -- |
1. Power seat and memory functions inoperative 2. Scan Tool Does Not Communicate with Low Speed GMLAN Device | ||||
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
Connector End View Reference
Power Seat Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
- 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.
- 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 all switch inputs to the MSM function normal, preform the Motor Control Circuit Test.
| ⇒ | If any of the switch parameters are Active, perform the Switch Circuit Test. |
| ⇒ | If any of the switch parameters are not Active, perform the 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 inoperative switch signal circuit terminal and the B+ circuit terminal E. Verify the related 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 memory seat module. |
| ⇒ | If not Active, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM. |
Motor Control Circuit Test
- Disconnect the (C3) harness connector at the memory seat module.
- Verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.
- Connect the (C3) harness connector at the memory seat module.
- Disconnect the (C1) harness connector at the appropriate seat adjuster motor assembly or seat recline motor.
- Connect a test lamp between the motor control circuit terminals of the inoperative motor.
- Verify that a test lamp illuminates while pressing the seat switch in both directions.
- If all circuits test normal, test or replace the inoperative seat 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 does not illuminate for both directions, test the motor control circuits for an open/high resistance. If the circuits test normal replace the MSM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for memory seat module replacement, setup, and programming |
