GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Monte Carlo 🢒 DTC 🢒 DTC B2650

Circuit Description

The body control module (BCM) monitors the headlamp high beam signal circuit for high beam activity. When the high beam headlamps are commanded on by the DRL relay or the headlamp dimmer switch the headlamp high beam signal circuit is pulled to ground. Battery positive voltage is applied to the DRL relay and the LH high beam headlamp from the DRL/EXT fuse and the RH high beam headlamp receives battery positive voltage from the EXT fuse.

Conditions for Running the DTC

The headlamps are not on and the DRL is not enabled.

Conditions for Setting the DTC
    • The BCM detects a short to ground or open in the headlamp high beam signal circuit. When the headlamps are off and the DRL are off.
    • The condition above must be present for more than 0.3 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B2650 in memory.

Conditions for Clearing the DTC
    • A current DTC B2650 will clear when the BCM no longer detects a short to ground or an open in the headlamp high beam signal circuit.
    • A history DTC B2650 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids
    • If the DTC B2650 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to ground in the headlamp high beam signal circuit.
       - An intermittent open in the headlamp high beam signal circuit.

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2
  1. Install a scan tool.
  2. Set the park brake.
  3. Place a bright incandescent light over the ambient light sensor.
  4. Turn the headlamp switch to the OFF position.
  5. Turn ON the ignition, with the engine OFF.
  6. With a scan tool, observe the Hi beam On switch parameter in the body control module data list.

Does the scan tool display active?

Go to Diagnostic Aids

Go to Step 3

3
  1. Remove the LH high beam headlamp.
  2. Using a test lamp connected to a known good ground, probe the headlamp high beam signal circuit at the LH high beam headlamp harness connector.

Does the test lamp illuminate?

Go to Step 5

Go to Step 4

4

  1. Disconnect the RH headlamp assembly.
  2. Using a test lamp connected to a known good ground, probe the headlamp high beam signal circuit at the RH headlamp harness connector.

Does the test lamp illuminate?

Go to Step 9

Go to Step 13

5

  1. Using a test lamp backprobe between the DRL headlamp high beam supply voltage circuit and the headlamp high beam signal circuit at the LH headlamp harness connector.
  2. Using a scan tool, command the DRL relay on.

Does the test lamp illuminate?

Go to Step 15

Go to Step 6

6
  1. Disconnect the headlamp assembly.
  2. Using a test lamp probe between the DRL headlamp high beam supply voltage circuit and the headlamp high beam signal circuit at the LH headlamp harness connector.
  3. Using a scan tool, command the DRL relay on.

Does the test lamp illuminate?

Go to Step 9

Go to Step 7

7
  1. Remove the DRL relay.
  2. Using a test lamp probe between battery positive voltage and the ground circuit of the DRL relay.

Does the test lamp illuminate?

Go to Step 8

Go to Step 12

8
  1. Install a fused 3A jumper in the DRL relay connector between the ground circuit and the DRL headlamp high beam supply voltage circuit.
  2. At the LH headlamp assembly, connect a test lamp between the DRL headlamp high beam supply voltage circuit and the headlamp high beam signal circuit.

Does the test lamp illuminate?

Go to Step 10

Go to Step 11

9

Inspect for a poor connection at the harness connectors of the LH high beam headlamp. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 16

10

Inspect for a poor connection at the DRL Relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

11

Repair a poor connection or an open in the DRL headlamp high beam supply voltage circuit. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

12

Repair a poor connection or an open in the ground circuit of the DRL Relay. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

13

Repair a poor connection or an open in the headlamp high beam signal circuit. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

14

Replace the DRL relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

15

Replace the LH high beam headlamp bulb.

Did you complete the repair?

Go to Step 17

--

16

Replace the LH headlamp assembly. Refer to Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement .

Did you complete the repair?

Go to Step 17

--

17
  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