Chevrolet Silverado / GMC Sierra. Manual — part 2694

circuit terminal 3. Verify the scan tool Driver Seat Recline Sensor parameter is greater than
4.65 volts.

If less than 4.65 volts, test the signal circuit for short to ground or an open/high
resistance. If the circuit tests normal, replace the MSM.

6. If all circuits test normal, test or replace the seat recline position sensor.

B2355, B2365, B2375

1. Ignition OFF, disconnect the harness connector X2 at the seat adjuster motor assembly.

2. Ignition OFF, test for less than 2 ohms of resistance between the low reference circuit

terminal 2 and ground.

If greater than 2 ohms, test the low reference circuit for an open/high resistance. If the
circuit tests normal, replace the MSM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 6 and

ground.

If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the MSM.

If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

4. Verify the appropriate scan tool Driver Seat Sensor parameter is less than 2.0 volts.

If greater than 2.0 volts, test the appropriate signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

Seat front vertical position sensor terminal 1

Seat rear vertical position sensor terminal 5

Seat horizontal position sensor terminal 3

5. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit

terminal 6. Verify the appropriate scan tool Driver Seat position sensor parameter is greater
than 4.65 volts.

Seat front vertical position sensor terminal 1

Seat rear vertical position sensor terminal 5

Seat horizontal position sensor terminal 3

If less than 4.65 volts, test the signal circuit for short to ground or an open/high
resistance. If the circuit tests normal, replace the MSM.

6. If all circuits test normal, test or replace the seat adjuster motor assembly.

B1850, B1860

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

1. Ignition OFF, disconnect the harness connector X2 at the seat lumbar motor assembly.

2. Ignition OFF, test for less than 2 ohms of resistance between the low reference circuit

terminal C and ground.

If greater than 2 ohms, test the low reference circuit for an open/high resistance. If the
circuit tests normal, replace the MSM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and

ground.

If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the MSM.

If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

4. Verify the appropriate scan tool Lumbar Sensor parameter is less than 2.0 volts.

If greater than 2.0 volts, test the appropriate signal circuit for a short to voltage. If the
circuit tests normal, replace the MSM.

Lumbar vertical position sensor terminal B

Lumbar horizontal position sensor terminal D

5. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit

terminal C. Verify the appropriate scan tool Lumbar Sensor parameter is greater than 4.65
volts.

Lumbar vertical position sensor terminal B

Lumbar horizontal position sensor terminal D

If less than 4.65 volts, test the signal circuit for short to ground or an open/high
resistance. If the circuit tests normal, replace the MSM.

6. If all circuits test normal, test or replace the lumbar motor assembly.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Front Seat Adjuster Replacement (Power)

Front Seat Lumbar Support Replacement

Front Seat Recliner Actuator Motor Replacement

Control Module References for MSM replacement, setup, and programming

DTC B3920 OR B3921

Diagnostic Instructions

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

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

DTC Descriptors

DTC B3920 01

Group 1 Seat Motors Circuit Shorted to Battery or Open

DTC B3920 02

Group 1 Seat Motors Circuit Shorted to Ground

Diagnostic Fault Information

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Driver Seat Front Vertical
Motor Down Control

B3920 02

1

B3920 01

-

Driver Seat Front Vertical
Motor Up Control

B3920 02

1

B3920 01

-

Driver Seat Rear Vertical
Motor Down Control

B3920 02

1

B3920 01

-

Driver Seat Rear Vertical
Motor Up Control

B3920 02

1

B3920 01

-

Driver Seat Horizontal Motor
Forward Control

B3920 02

1

B3920 01

-

Driver Seat Horizontal Motor
Rearward Control

B3920 02

1

B3920 01

-

Driver Seat Recline Motor
Forward Control

B3920 02

1

B3920 01

-

Driver Seat Recline Motor
Rearward Control

B3920 02

1

B3920 01

-

Driver Seat Lumbar Motor
Down Control

B3920 02

1

B3920 01

-

Driver Seat Lumbar Motor
Forward Control

B3920 02

1

B3920 01

-

Driver Seat Lumbar Motor Up

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Power Seats - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado