GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Rendezvous - FWD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC B3840

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 B3840 Park Lamp Signal Circuit Low

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 an open or a short to ground in the park lamp supply voltage circuit with the headlamp switch in either the PARK position or the HEAD position.

Action Taken When the DTC Sets

The BCM stores DTC B3840 in memory.

Conditions for Clearing the MIL/DTC
    • A current DTC B3840 clears if the BCM no longer detects an open or a short to ground.
    • A history DTC B3840 clears after 100 consecutive ignition cycles.
    • The BCM receives the clear code command from the scan tool.

Diagnostic Aids
    • If the DTC B3840 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • An intermittent open or short to ground 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. Turn ON the park lamps.
  4. 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 ON/ ACTIVE?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the battery positive voltage circuit of the park lamp relay switch and the park lamps supply voltage circuit of the park lamp relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Turn ON the park lamps.
  5. With a scan tool, observe the Park Lamp Monitor parameter.

Does the scan tool indicate that the Park Lamp Monitor parameter is ON/ACTIVE?

Go to Step 6

Go to Step 4

4

Test the battery positive voltage circuit of the park lamp relay for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 5

5

Test the park lamp supply voltage circuit for a high resistance, a short to ground, or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 7

6

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 10

Go to Step 8

7

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 10

Go to Step 9

8

Replace the park lamp relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 10

--

9

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

Did you complete the replacement?

Go to Step 10

--

10
  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