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Chevrolet Silverado / GMC Sierra. Manual - part 2698
and ground.
Vertical lumbar terminal B
Horizontal lumbar terminal D
If greater than the specified range, test the control circuit for a short to voltage or an
open/high resistance. If circuit tests normal, replace the lumbar switch.
4. Connect a test lamp between affected control circuit terminals listed.
Vertical lumbar terminal A to terminal B
Horizontal lumbarterminal C to terminal D
5. Operate the affected switch in both directions. The test lamp should turn ON when the
switch is pressed in both directions.
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 lumbar switch.
6. If all circuits test normal, test or replace the lumbar support.
Component Testing
Seat Adjuster Switch Test
1. Ignition OFF, disconnect the harness connector at the seat adjuster switch.
2. Test for infinite resistance between each control terminal and the B+ terminal with the
switch in the open position.
If less than the specified value, replace the seat adjuster switch.
3. Test for less than 1 ohm between each control terminal and the B+ terminal with the switch
in the closed position.
If greater than the specified range, replace the seat adjuster switch.
4. Test for less than 1 ohm between each control terminal and the ground terminal with the
switch in the open position.
If greater than the specified range, replace the seat adjuster switch.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Power Seat Switch Replacement
Front Seat Adjuster Replacement (Power)
Lumbar Switch Replacement
Front Seat Lumbar Support Replacement
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Front Seat Recliner Actuator Motor Replacement
POWER SEAT INOPERATIVE (W/MEMORY)
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+
1
1
-
-
B+
2
2
-
-
Front Vertical
Down Switch
Signal
2
1
B1735 01, B1740 01,
B1745 01, B1750 01,
B1755 01, B1760 01,
B1815 01, B1820 01
-
Front Vertical Up
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
-
Lumbar Down
Switch Signal
2
1
B1735 01, B1740 01,
B1745 01, B1750 01,
B1755 01, B1760 01,
B1815 01, B1820 01
-
Lumbar Up
Switch Signal
2
1
B1735 01, B1740 01,
B1745 01, B1750 01,
B1755 01, B1760 01,
-
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
B1815 01, B1820 01
Lumbar Forward
Switch Signal
2
1
B1735 01, B1740 01,
B1745 01, B1750 01,
B1755 01, B1760 01,
B1815 01, B1820 01
-
Lumbar Rearward
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
-
Rear Vertical Up
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
-
Front Vertical
Motor Front
Down Control
B3920 02
1
B3920 01
B2355 5A
Front Vertical
Motor Front Up
Control
B3920 02
1
B3920 01
B2355 5A
Horizontal Motor
Forward Control
B3920 02
1
B3920 01
B2375 5A
Horizontal Motor
Rearward Control
B3920 02
1
B3920 01
B2375 5A
Lumbar
Horizontal Motor
Forward Control
B3920 02
1
B3920 01
B1850 5A
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Circuit/System Description
The 8-way power driver seat with memory is controlled by the memory seat module (MSM). The
low current battery supply circuit from the DSM 10A fuse supplies the logic power and reference
voltages to the MSM. The high current battery supply circuit from the DRIVER SEAT 2 25A
circuit breaker supplies the MSM power rail 1 which is used to drive the power seat motors,
adjustable pedals motor, and seat heater elements with heated seats only. The MSM supplies a
battery voltage reference circuit to the seat adjuster and lumbar switches. The switch signal
circuits are referenced from ground within the MSM and when a switch is activated the signal
circuit goes high. Each seat adjuster motor is controlled by the MSM through 2 motor control
circuits. While the seat adjuster motors are in an inactive state the motor control circuits are
closed to ground circuit contacts within the MSM. The MSM operates the seat adjuster motors by
switching one of a motors control circuits to battery voltage. The seat adjuster motors are
bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster
motor control circuits is switched to battery voltage while the other remains grounded.
Lumbar
Horizontal Motor
Rearward Control
B3920 02
1
B3920 01
B1850 5A
Lumbar Vertical
Motor Down
Control
B3920 02
1
B3920 01
B1860 5A
Lumbar Vertical
Motor Up Control
B3920 02
1
B3920 01
B1860 5A
Rear Vertical
Motor Rear Down
Control
B3920 02
1
B3920 01
B2365 5A
Rear Vertical
Motor Rear Up
Control
B3920 02
1
B3920 01
B2365 5A
Recline Motor
Forward Control
B3920 02
1
B3920 01
B1825 5A
Recline Motor
Rearward Control
B3920 02
1
B3920 01
B1825 5A
Ground
-
-
-
-
Ground
-
-
-
-
1. Driver power seat, lumbar, and memory functions inoperative
2. Scan Tool Does Not Communicate with Low Speed GMLAN Device
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Content .. 2696 2697 2698 2699 ..