GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Monte Carlo 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B2651

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 enabled.

Conditions for Setting the DTC
    • The BCM detects a short to ground or open in the of 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 B2651 in memory.

Conditions for Clearing the DTC
    • A current DTC B2651 will clear when the BCM no longer detects a short to ground or an open in the high beam signal circuit.
    • A history DTC B2651 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids
    • If the DTC B2651 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 high beam signal circuit.
       - An intermittent open in the 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. Place a bright incandescent light over the ambient light sensor.
  3. Turn the headlamp switch to the OFF position.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, command the DRL relay on.

Does the LH and RH high beam headlamps illuminate?

Go to Diagnostic Aids

Go to Step 3

3
  1. Remove the RH high beam headlamp.
  2. Using a test lamp connected to a known good ground, probe the battery positive voltage feed circuit at the RH 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 battery positive voltage feed circuit at the RH headlamp harness connector.

Does the test lamp illuminate?

Go to Step 7

Go to Step 9

5

  1. Using a test lamp probe between battery positive voltage and the headlamp high beam signal circuit at the RH headlamp harness connector.
  2. Using a scan tool, command the DRL relay on.

Does the test lamp illuminate?

Go to Step 8

Go to Step 6

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

Does the test lamp illuminate?

Go to Step 7

Go to Step 10

7

Inspect for a poor connection at the harness connectors of the RH 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 13

Go to Step 12

8

Inspect for a poor connection at the RH 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 13

Go to Step 11

9

Repair an open or a short to ground in the battery positive voltage feed of the RH high beam headlamp. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

10

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 13

--

11

Replace the RH high beam headlamp bulb.

Did you complete the repair?

Go to Step 13

--

12

Replace the RH 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 13

--

13
  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