GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

The daytime running lamp (DRL) system will not work if the parking brake is applied. The system is designed to work only when the engine is running and the parking brake is released. If the parking brake circuit is shorted to ground or the switch stays closed when the engine is running, the DRL system will not work.

Step

Action

Values

Yes

No

1

Turn the headlamps ON with the headlamp switch.

Do the headlamps work?

--

Go to Step 3

Go to Step 2

2

Repair the regular headlamp system before completing this diagnostic table.

Does the daytime running lamp (DRL) system work after the headlamps have been repaired?

--

System OK

Go to Step 3

3

Check fuse Ef4 and F1.

Is fuse Ef4 and F1 blown?

--

Go to Step 4

Go to Step 5

4

  1. Check for a short circuit and repair if necessary.
  2. Replace fuse Ef4 or F1.

Is the repair complete?

--

System OK

--

5

  1. Turn the ignition ON.
  2. Check the voltage at fuse Ef4 and F1.

Does the voltage equal the specified value?

11-14 V

Go to Step 7

Go to Step 6

6

Repair the power supply circuit for fuse Ef4 and F1.

Is the repair complete?

--

System OK

--

7

  1. Disconnect the electrical connector from the DRL module.
  2. Turn the ignition ON.
  3. Check the voltage at terminal 1 of the DRL module.

Is the voltage equal to the specified value?

11-14 V

Go to Step 9

Go to Step 8

8

Repair the open circuit between fuse Ef4 and terminal 1 of the DRL module connector.

Is the repair complete?

--

System OK

--

9

With the DRL module still disconnected, use an ohmmeter to check the resistance between ground and terminal 5 of the DRL module connector.

Is the resistance equal to the specified value?

0 ohms

Go to Step 11

Go to Step 10

10

Repair the circuit between ground and terminal 5 of the DRL module connector.

Is the repair complete?

--

System OK

--

11

  1. Release the parking brake.
  2. Turn the ignition switch ON.
  3. Observe the parking brake indicator lamp.

Is the parking brake indicator lamp ON?

--

Go to Step 12

Go to Step 15

12

Disconnect the electrical connector to the parking brake lever switch.

Is the parking brake indicator lamp still ON?

--

Go to Step 13

Go to Step 14

13

Repair the short to ground in the parking brake circuit.

Is the repair complete?

--

System OK

--

14

Replace the parking brake lever switch.

Is the repair complete?

--

System OK

--

15

  1. Make sure the headlamps are turned OFF.
  2. With the DRL module disconnected, turn the ignition ON.
  3. Check the voltage at terminal 6 of the DRL module.

Is the voltage equal to the specified value?

0 V

Go to Step 17

Go to Step 16

16

Repair the open between fuse F13 and terminal 6 of the DRL module.

Is the repair complete?

--

System OK

--

17

Replace the DRL module.

Is the repair complete?

--

System OK

--