GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Tahoe - 2WD 🢒 DTC 🢒 DTC B3821

Circuit Description

Battery positive voltage is supplied to the left rear power window switch and the up and down relays through the window lockout signal circuit. If the window lockout function is disabled, the body control module (BCM) supplies battery positive voltage to the switch and relays and the left rear window operates normally. If the window lockout function is enabled, the BCM will not supply battery positive voltage to the switch and relays and the left rear window will be inoperative unless it is operated from the driver power window switch.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3821 Left Rear Window Relay Power Circuit

Conditions for Running the DTC
    • Battery voltage is between 9-16 volts.
    • The window lockout function is disabled

Conditions for Setting the DTC
    • The window lockout function is disabled and the window lockout signal circuit is shorted to ground.
    • The above condition must be met for 250 milliseconds.

Action Taken When the DTC Sets

The left rear power window will be inoperative from both the driver and passenger power window switches.

Conditions for Clearing the DTC

When the fault is no longer present, the BCM changes the current DTC to a history DTC. The BCM will clear the history DTC after 50 fault free ignition cycles.

Step

Action

Yes

No

Schematic Reference: Power Window Schematics

Connector End View Reference: Power Door Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Disable the window lockout function.
  4. With a scan tool, command the left rear power window UP and DOWN.

Does the left rear power window operate UP and DOWN with each command?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the left rear power window switch.
  3. Turn ON the ignition, with the engine OFF.
  4. Ensure the window lockout function is disabled.
  5. Probe the window lockout signal circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

Test the window lockout signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 7

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7
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK