Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2009TAHOE BASE, 4.8 CREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 56 (POWER SEAT SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B3920 OR B3921CIRCUIT/SYSTEM TESTING
2009 Chevrolet Tahoe Base, 4.8 C
Circuit/System Testing
2009 Chevrolet Tahoe Base, 4.8 CSECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the C1 harness connector at the MSM.
- Ignition ON, verify that a test does not illuminate between any of the following motor control circuits and ground:
- Front vertical motor terminal 12
- Front vertical motor terminal 13
- Rear vertical motor terminal 15
- Rear vertical motor terminal 16
- Seat horizontal motor terminal 9
- Seat horizontal motor terminal 10
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Test for infinite resistance between the following motor control circuits and ground:
- Front vertical motor terminal 12
- Front vertical motor terminal 13
- Rear vertical motor terminal 15
- Rear vertical motor terminal 16
- Seat horizontal motor terminal 9
- Seat horizontal motor terminal 10
- If less than infinite resistance, test the motor control circuit for a short to ground.
- Test for greater resistance values than specified between the following motor control circuits:
- 1 ohm for front vertical motor terminal 12 and terminal 13
- 1 ohm for rear vertical motor terminal 15 and terminal 16
- 10 ohms for seat horizontal motor terminal 9 and terminal 10
- If less than the specified resistance, test the control circuits for a short together or shorted motor.
- Ignition OFF, disconnect the C4 harness connector at the MSM.
- Ignition ON, verify that a test does not illuminate between any of the following motor control circuits and ground:
- Lumbar vertical motor terminal 1
- Lumbar vertical motor terminal 2
- Lumbar horizontal motor terminal 12
- Lumbar horizontal motor terminal 13
- Seat recline motor terminal 15
- Seat recline motor terminal 16
- Adjustable pedal motor terminal 9
- Adjustable pedal motor terminal 10
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Test for infinite resistance between the following motor control circuits and ground:
- Lumbar vertical motor terminal 1
- Lumbar vertical motor terminal 2
- Lumbar horizontal motor terminal 12
- Lumbar horizontal motor terminal 13
- Seat recline motor terminal 15
- Seat recline motor terminal 16
- Adjustable pedal motor terminal 9
- Adjustable pedal motor terminal 10
- If less than infinite resistance, test the motor control circuit for a short to ground.
- Test for greater resistance values than specified between the following motor control circuits:
- 10 ohms for lumbar horizontal motor terminal 12 and terminal 13
- 1 ohm for recline motor terminal 15 and terminal 16
- If less than the specified resistance, test the control circuits for a short together or shorted motor.
- If all circuits test normal, replace the MSM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.