GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) monitors the activity of the park lamp relay switch with the headlamp switch in either the PARK position or the HEAD position.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3841 Park Lamp Signal Circuit High

Conditions for Running the DTC

Voltage supplied to the module is in the normal operating voltage range, approximately 10-16 volts.

Conditions for Setting the DTC

The BCM detects a short to voltage in the park lamp supply voltage circuit when the headlamp switch is in the OFF position.

Action Taken When the DTC Sets

The BCM stores DTC  B3841 in memory.

Conditions for Clearing the MIL/DTC

    • A current DTC B3841 clears if the BCM no longer detects a short to battery positive voltage.
    • A history DTC B3841 clears after 100 consecutive ignition cycles.
    • The BCM receives the clear code command from the scan tool.

Diagnostic Aids

    • If the DTC B3841 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • An intermittent short to battery positive voltage in the following locations may cause an intermittent malfunction to occur:
       - The park lamp supply voltage circuit
       - The park lamp relay
       - The BCM

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Park Lamp Monitor parameter in the body control module (BCM) data list.

Does the scan tool indicate that the Park Lamp Monitor parameter is OFF/INACTIVE?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Remove the park lamp relay.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Park Lamp Monitor parameter.

Does the scan tool indicate that the park Lamp Monitor parameter is OFF/INACTIVE?

Go to Step 5

Go to Step 4

4

Test the park lamp supply voltage circuit for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 6

5

Inspect for a poor connection at the park lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 7

6

Inspect for a poor connection at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 8

7

Replace the park lamp relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 9

--

8

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 9

--

9

  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