Chevrolet Silverado / GMC Sierra. Manual — part 2699
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
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Install a scan tool and display the MSM switch inputs.
2. Verify that none of the power seat switch parameters are Active while in an inactive state.
If not the specified value, refer to the Power Seat Switch Circuit Test below.
3. Verify that the power seat switch parameters are Active while the switch is pressed.
If not the specified value, refer to the Power Seat Switch Circuit Test below.
4. Verify that none of the lumbar switch parameters are Active while in an inactive state.
If not the specified value, refer to the Lumbar Switch Circuit Test below.
5. Verify that the lumbar switch parameters are Active while the switch is pressed.
If not the specified value, refer to the Lumbar Switch Circuit Test below.
6. If the switch inputs to the MSM function normal, refer to the affected Motor Control Circuit
Test below.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Circuit/System Testing
Power Seat Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the power seat switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal E
and ground.
If the test lamp does not illuminate, test the B+ reference circuit for a short to ground
or an open/high resistance.
3. Verify the scan tool power seat switch parameters are Inactive.
If not the specified values, test the affected signal circuit terminal listed for a short to
voltage. If the circuit tests normal, replace the MSM.
Front vertical down switch terminal K
Front vertical up switch terminal A
Horizontal forward switch terminal D
Horizontal rearward switch terminal C
Rear vertical down switch terminal J
Rear vertical up switch terminal F
Recline forward switch terminal H
Recline rearward switch terminal G
4. Install a 3A fused jumper wire between the affected signal circuit terminal listed and the B+
reference circuit terminal E. Verify the affected scan tool power seat switch parameter is
Acitve.
Front vertical down switch terminal K
Front vertical up switch terminal A
Horizontal forward switch terminal D
Horizontal rearward switch terminal C
Rear vertical down switch terminal J
Rear vertical up switch terminal F
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.
5. If all circuits test normal, test or replace the power seat switch.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Lumbar Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the lumbar switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ reference circuit terminal G
and ground.
If the test lamp does not illuminate, test the B+ reference circuit for a short to ground
or an open/high resistance.
3. Verify the scan tool lumbar switch parameters are Inactive.
If not the specified values, test the affected signal circuit terminal listed for a short to
voltage. If the circuit tests normal, replace the MSM.
Lumbar down switch terminal K
Lumbar up switch terminal A
Lumbar forward switch terminal D
Lumbar rearward switch terminal C
4. Install a 3A fused jumper wire between the affected signal circuit terminal listed and the B+
reference circuit terminal G. Verify the affected scan tool lumbar switch parameter is
Acitve.
Lumbar down switch terminal K
Lumbar up switch terminal A
Lumbar forward switch terminal D
Lumbar rearward switch terminal C
If not the specified value, test the signal circuit for an open/high resistance. If the
circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the lumbar switch.
Seat Adjuster Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the seat adjuster assembly.
2. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed
and ground.
Rear vertical terminal 1
Front vertical terminal 2
Horizontal terminal 3
If greater than the specified range, test the control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the MSM.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
3. Ignition OFF, test for less than 1.0 ohm between the affected control circuit terminal listed
and ground.
Rear vertical terminal 4
Front vertical terminal 5
Horizontal terminal 6
If greater than the specified range, test the control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the MSM.
4. Connect a test lamp between the affected control circuit terminals listed.
Rear vertical terminal 1 to terminal 4
Front vertical terminal 2 to terminal 5
Horizontal terminal 3 to terminal 6
5. Command the affected function in both directions with a scan tool. The test lamp should
turn ON when commanding the affected function in both states.
If the test lamp remains OFF during either of the commands, test for a short to ground
on either control circuit. If the circuits test normal, replace the MSM.
6. If all circuits test normal, test or replace the seat adjuster.
Recline Motor Control Circuit Test
1. Ignition OFF, disconnect the harness connector at the recline motor.
2. Ignition OFF, test for less than 1.0 ohm between the control circuit terminal A and ground.
If greater than the specified range, test the control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the MSM.
3. Ignition OFF, test for less than 1.0 ohm between the control circuit terminal B and ground.
If greater than the specified range, test the control circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the MSM.
4. Connect a test lamp between control circuit terminal A and control circuit terminal B.
5. Command the recline Forward and Rearward with a scan tool. The test lamp should turn
ON when commanding the Forward and Rearward states.
If the test lamp remains OFF during either of the commands, test for a short to ground
on either control circuit. If the circuits test normal, replace the MSM.
6. If all circuits test normal, test or replace the recliner motor.
Lumbar Motor Control Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the lumbar adjuster assembly.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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