Power Seat Malfunction (With Memory)
| Power Seat Malfunction (With Memory) |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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Seat Memory Control Module B+ Terminal 1 X4
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2
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2
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-
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-
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Seat Memory Control Module B+ Terminal 5 X4
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B242A 02, B2425 0D, B2430 0D, 1, 3
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B242A 02, B2425 0D, B2430 0D, 1, 3
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-
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-
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Front Vertical Up Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Front Vertical Down Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Rear Vertical Up Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Rear Vertical Down Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Horizontal Forward Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Horizontal Rearward Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Recline Forward Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Recline Rearward Switch Signal
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B1735 02, B1740 02, B1745 02, B1750 02, B1755 02, B1760 02, B1815 02, B1820 02
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1
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-
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-
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Driver Seat Front Vertical Motor Down Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Front Vertical Motor Up Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Horizontal Motor Forward Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Horizontal Motor Rearward Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Rear Vertical Motor Down Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Rear Vertical Motor Up Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Recline Motor Forward Control
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B3920 02
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1
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B3920 01
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B3920 00
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Driver Seat Recline Motor Rearward Control
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B3920 02
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1
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B3920 01
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B3920 00
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Seat Memory Control Module Ground Terminal 3 X4
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-
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1, 2
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-
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-
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Seat Memory Control Module Ground Terminal 6 X4
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-
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1, 2
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-
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-
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1. Power seat and memory functions inoperative
2. Scan Tool Does Not Communicate with Low Speed GMLAN Device 3. Heated seats are inoperative |
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| Circuit/System Description |
Battery voltage is supplied at all times to the seat memory control module through a 25 A fuse located in the I/P fuse block. This voltage is used by the module for logic power. Battery positive voltage is also supplied at all times to the seat memory control module through a 25 A circuit breaker. This voltage is connected to a power rail internal to the seat memory control module and is used to drive the power seat motors and the seat heater elements on vehicles equipped with heated seats. Each seat motor is controlled by the seat memory control module through 2 motor control circuits. The seat memory control module 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 V. The seat memory control module checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat motors.
All motors are reversible. For example, when the seat switch is operated to move the entire seat forward, the switch signal circuit from the seat memory control module is pulled low indicating the entire seat forward command. In response to this signal, the seat memory control module 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
Driver Seat Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Memory Seats Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool Reference
Control Module References for scan tool information
| Circuit/System Verification |
| 1. |
Ignition ON, observe the scan tool Seat Memory Control Module seat switch parameters listed below while pressing the appropriate seat switch. The reading should change between Inactive and Forward/Rearward or Up/Down.
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Driver Seat Horizontal Switch
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Driver Seat Cushion Front Vertical Switch
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Driver Seat Cushion Rear Vertical Switch
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Driver Seat Back Switch
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| 2. |
If the reading does not change between the specified values, refer to the Driver Seat Switch Circuit Test.
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| 3. |
If all seat switch inputs to the K40 seat memory control module function normal, refer to the Seat Motor Control Circuit Test.
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| Circuit/System Testing |
Driver Seat Switch Circuit Test
| 1. |
Ignition OFF, disconnect the harness connector at the S64D driver seat adjuster switch.
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| 2. |
Test for less than 10 Ω between the ground circuit terminal E and ground.
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| 3. |
If greater than the specified range, test the ground circuit for an open/high resistance.
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| 4. |
Ignition ON, verify that the scan tool seat switch parameters listed below are Inactive:
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Driver Seat Horizontal Switch
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Driver Seat Cushion Front Vertical Switch
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Driver Seat Cushion Rear Vertical Switch
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Driver Seat Back Switch
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| 5. |
If not the specified value, test the appropriate signal circuit listed below for a short to ground. If the circuit tests normal, replace the K40 seat memory control module.
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Front vertical upward switch terminal A (LHD)
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Front vertical upward switch terminal K (RHD)
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Front vertical downward switch terminal K (LHD)
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Front vertical downward switch terminal A (RHD)
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Rear vertical upward switch terminal F (LHD)
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Rear vertical upward switch terminal J (RHD)
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Rear vertical downward switch terminal J (LHD)
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Rear vertical downward switch terminal F (RHD)
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Horizontal forward switch terminal D
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Horizontal rearward switch terminal C
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Recline forward switch terminal H
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Recline rearward switch terminal G
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| 6. |
Install a 3 A fused jumper wire between the ground circuit terminal B and the appropriate signal circuit terminal listed below. Verify the appropriate scan tool seat switch parameter is Forward/Rearward or Up/Down.
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Front vertical upward switch terminal A (LHD)
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Front vertical upward switch terminal K (RHD)
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Front vertical downward switch terminal K (LHD)
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Front vertical downward switch terminal A (RHD)
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Rear vertical upward switch terminal F (LHD)
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Rear vertical upward switch terminal J (RHD)
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Rear vertical downward switch terminal J (LHD)
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Rear vertical downward switch terminal F (RHD)
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Horizontal forward switch terminal D
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Horizontal rearward switch terminal C
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Recline forward switch terminal H
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Recline rearward switch terminal G
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| 7. |
If not the specified value, test the signal circuit for a short to voltage an open/high resistance. If the circuit tests normal, replace the K40 seat memory control module.
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| 8. |
If all circuits test normal, test or replace the S64D driver seat aduster switch.
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Seat Motor Control Circuit Test
| 1. |
Ignition OFF, disconnect the X4 harness connector at the K40 seat memory control module.
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| 2. |
Test for less than 5 Ω between the ground circuit terminals listed below and ground:
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Terminal 3
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Terminal 6
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| 3. |
If less than the specified range, test the ground circuit for an open/high resistance.
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| 4. |
Ignition ON, verify that a test lamp illuminates between the B+ circuit terminals listed below and ground:
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Terminal 1
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Terminal 5
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| 5. |
If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
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| 6. |
Connect the X4 harness connector at the K40 seat memory control module and disconnect the harness connector at the appropriate seat motor listed below:
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M50 seat front vertical motor
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M55 seat rear vertical motor
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M51 seat horizontal motor
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M56 seat back recline motor
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| 7. |
Connect a test lamp between control circuit terminal 1 and control circuit terminal 5.
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| 8. |
Ignition ON, command the 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. |
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| 9. |
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 K40 seat memory control module.
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| 10. |
If all circuits test normal, test or replace the seat motor.
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| Component Testing |
Driver Seat Switch
| 1. |
Ignition OFF, disconnect the harness connector at the S64D driver seat adjuster switch.
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| 2. |
Test for infinite resistance between the ground terminal E and each signal terminal listed below with the switch in the open position.
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Front vertical upward switch terminal A (LHD)
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Front vertical upward switch terminal K (RHD)
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Front vertical downward switch terminal K (LHD)
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Front vertical downward switch terminal A (RHD)
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Rear vertical upward switch terminal F (LHD)
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Rear vertical upward switch terminal J (RHD)
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Rear vertical downward switch terminal J (LHD)
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Rear vertical downward switch terminal F (RHD)
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Horizontal forward switch terminal D
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Horizontal rearward switch terminal C
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Recline forward switch terminal H
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Recline rearward switch terminal G
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| 3. |
If not the specified value, replace the S64D driver seat adjuster switch.
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| 4. |
Test for less than 1 Ω between the ground terminal E and each signal terminal listed below with the appropriate switch in the closed position.
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Front vertical upward switch terminal A (LHD)
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Front vertical upward switch terminal K (RHD)
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Front vertical downward switch terminal K (LHD)
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Front vertical downward switch terminal A (RHD)
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Rear vertical upward switch terminal F (LHD)
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Rear vertical upward switch terminal J (RHD)
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Rear vertical downward switch terminal J (LHD)
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Rear vertical downward switch terminal F (RHD)
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Horizontal forward switch terminal D
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Horizontal rearward switch terminal C
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Recline forward switch terminal H
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Recline rearward switch terminal G
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| 5. |
If greater than the specified range, replace the S64D driver seat adjuster switch.
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Seat Motor
| 1. |
Ignition OFF, disconnect the harness connector at the appropriate seat motor listed below:
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M50 Front Vertical Motor
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M55 Rear Vertical Motor
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M51 Horizontal Motor
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M56 Recline Motor
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| 2. |
Install a 30 A fused jumper wire between control terminal 1 and 12 V. Momentarily install a jumper wire between control terminal 5 and ground. The seat motor should momentarily perform the appropriate FORWARD/REARWARD/UP/DOWN function. |
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| 3. |
If the function does not perform as specified, replace the seat motor.
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| 4. |
Reverse the polarity of jumper wires. The a seat motor should perform in the opposite direction.
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| 5. |
If the function does not perform as specified, replace the seat motor.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Driver or Passenger Seat Adjuster Switch Replacement (Driver/Passenger Seat 4-Way Hybrid)
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Front Seat Adjuster Motor Replacement (Driver or Passenger Seat 8-Way Power)
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Front Seat Recliner Actuator Motor Replacement (Driver or Passenger Seat 8-Way Power)
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Control Module References
for seat memory control module replacement, setup, and programming
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