GM Service Manual Online
For 1990-2009 cars only

Refer to Exterior Lights Schematics .

Circuit Description

The parklamps are controlled by the turn/headlamp switch. Positive battery voltage is supplied to the switch through the EXT LP fuse. When the turn/headlamp switch is placed in the park or head position, battery voltage is supplied to the park lamps. The body control module is also connected to the parklamp circuit to sense whether or not the parklamps turn on when the lowbeam or highbeam headlamps are turned on. The BCM also uses the parklamp battery supply to power the instrument panel dimmer output circuit. If the BCM senses that the lowbeam or highbeam headlamps are on and the parklamp input is not active, DTC B2662 sets.

Conditions for Running the DTC

    • The ignition switch is on.
    • The lowbeam or highbeam headlamps are on.

Conditions for Setting the DTC

The parklamp input is inactive for 1 second.

Action Taken When the DTC Sets

DTC B2662 is stored in the BCM memory.

Conditions for Clearing the DTC

    • A current DTC B2662 will clear when the malfunction is no longer present and the ignition switch is cycled.
    • All BCM history codes clear after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.
    • A scan tool can be used to clear the DTC.

Diagnostic Aids

    • The low or highbeam headlamps must be on in order to set this DTC.
    • An open EXT LP fuse will set this code.
    • If the DTC is a history DTC, the problem may be intermittent. Try performing tests while wiggling the wiring and connectors. This can often cause the malfunction to appear.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Lighting Systems ?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the PARK LAMP INPUT parameter in the LAMP STATUS data list.
  4. Turn the lowbeam headlamps on.
  5. Return the headlamp switch to the off position.

Does the scan tool display toggle between on and off?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Are the parklamps operating normally when the headlamp switch is turned on and then off?

Go to Step 5

Go to Step 4

4

Inspect the EXT LAMP fuse.

Is the fuse good?

Go to Step 7

Go to Step 8

5

Test the signal circuit of the turn/headlamp switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 6

6

Inspect for poor connections at the harness connector of the BCM. 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 12

Go to Step 10

7

Test the battery supply circuit of the turn/headlamp switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

8

Test the battery supply circuit of the turn/headlamp switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

--

9

Inspect for poor connections at the harness connector of the turn/headlamp switch. 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 12

Go to Step 11

10

Important: Perform the set up procedure for the body control module.

Replace the body control module. Refer to Body Control Module Replacement .

Did you complete the replacement?

Go to Step 12

--

11

Replace the turn/headlamp switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 12

--

12

  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