Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

If the DTC B3840 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
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

DTC B3840

Step	Action	Yes	No
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems.
1	Did you perform the Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Install a scan tool. Turn ON the ignition, with the engine OFF. Turn ON the park lamps. With a scan tool, observe the park lamp monitor parameter in the Body Control Module 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	Turn OFF the ignition. 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. Turn ON the ignition, with the engine OFF. Turn ON the park lamps. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 body control module. 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 10	Go to Step 9
8	Replace the park lamp relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) in Wiring Systems. Did you complete the replacement?	Go to Step 10	-
9	IMPORTANT: Perform the set up procedure for the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems. Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	Go to Step 10	-
10	Use the scan tool in order to clear the DTCs. 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