GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Body 🢒 Instrument Panel, Gages, and Console 🢒 Chime Inoperative

Diagnostic Aids

Fuse EF20 controls the instrument cluster lighting and the right side tail lamps, parking lamps, and marker lamps. It also provides the input to the chime module for the lighting reminder.

Test Description

The number below refers to the step number on the diagnostic table.

  1. The chime module is under the instrument panel on the let side.

Step

Action

Values

Yes

No

1
  1. Turn the parking lamps and the tail lamps ON.
  2. Verify that the parking and tail lamps are working on the right side of the vehicle.

Are the parking lamps and tail lamps working on the right side of the vehicle?

--

Go to Step 3

Go to Step 2

2

Repair the parking lamps and the tail lamps before completing this diagnostic table.

Does the headlamps-on reminder chime in the ISU work after the parking lamps and the tail lamps have been repaired?

--

System OK

Go to Step 3

3

  1. Disconnect the ISU electrical connector.
  2. Turn the headlamps ON.
  3. Measure the voltage at terminal B27 of the ISU.

Is the voltage near the specified range?

11-14 V

Go to Step 7

Go to Step 4

4
  1. Remove the dimmer switch from the instrument panel for testing, but do not disconnect the electrical connector.
  2. Turn the headlamps ON.
  3. Measure the voltage at terminal 3 of the three-pin dimmer switch connector.

Is the voltage near the specified range?

11-14 V

Go to Step 5

Go to Step 6

5

Repair the open circuit wire between the dimmer switch connector terminal 3 and the ISU connector terminal B27.

Is the repair complete?

--

System OK

--

6

Repair the open circuit between fuse EF21 and the dimmer switch.

Is the repair complete?

--

System OK

--

7

Use an ohmmeter to Measure the continuity between ground and terminal B27 of the ISU connector.

Does the ohmmeter indicate the specified value?

0 ohms

Go to Step 9

Go to Step 8

8

Repair the open circuit between ground and terminal B27 of the ISU connector.

Is the repair complete?

--

System OK

--

9
  1. Open the driver door.
  2. Connect an ohmmeter between ground and terminal A8 of the ISU connector.

Does the ohmmeter indicate the specified value?

0 ohms

Go to Step 11

Go to Step 10

10

Repair the open circuit between ground and terminal A8 of the ISU connector. The door open switch should be closed when the door is open.

Is the repair complete?

--

System OK

--

11

Replace the ISU. Refer to Intelligent Switching Unit Replacement in Body Control System.

Is the repair complete?

--

System OK

--