GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Optra 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake Warning System Check

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. When the ignition is turned ON, the brake warning lamp should initially illuminate and then dim for antilock brake system (ABS) equipped vehicles. This is done as a bulb check. On vehicles that are not equipped with ABS, the brake warning lamp should only illuminate when either the brake fluid reservoir is low or the parking brake is applied.

    2.

  2. The brake fluid level switch is a normally open switch. If the brake warning lamp is off after disconnecting the switch, the brake fluid level switch is stuck closed.

    3.

  3. If the brake warning lamp is still ON after disconnecting the parking brake switch, there is a short to ground in the wire to the parking brake switch.

    4.

  4. If the other checks have been properly performed and the brake warning lamp is off after disconnecting the electronic brake control module (EBCM) J1 connector, the EBCM is faulty.

    5.

  5. If the brake warning lamp does not operate while performing any of the functions, the fault should be in the ignition feed to the circuit.

    6.

  6. This step determines if the problem is in the ignition feed to the circuit or in the instrument cluster.

    7.

  7. The brake warning lamp should illuminate when jumpering the parking brake connector to ground.

    8.

  8. If the brake warning lamp is ON after jumpering the brake fluid level switch terminals, the switch is faulty.

Step

Action

Values

Yes

No

1

Turn the ignition ON.

Is the brake warning lamp always ON?

--

Go to Step 2

Go to Step 18

2

Inspect the antilock brake system (ABS) warning lamp.

Is the ABS warning lamp also ON?

--

Go to Step 3

Go to Step 4

3

Use a scan tool to check for DTCs and follow the procedures for any DTCs found.

Is the lamp still ON?

--

Go to Step 4

System OK

4

Release the parking brake fully.

Is the lamp OFF?

--

System OK

Go to Step 5

5

Check the brake fluid level.

Is the fluid level OK?

--

Go to Step 7

Go to Step 6

6
  1. Fill the brake fluid reservoir with clean DOT 3 equivalent hydraulic fluid.
  2. Replace the cap on the fluid reservoir.

Is the lamp ON?

--

Go to Step 7

System OK

7

Disconnect the harness connector from the brake fluid level switch.

Is the lamp ON?

--

Go to Step 9

Go to Step 8

8

Replace the brake fluid level switch.

Did you complete the replacement?

--

System OK

--

9

  1. Connect the brake fluid level switch.
  2. Disconnect the parking brake switch.

Is the lamp ON?

--

Go to Step 11

Go to Step 10

10

Replace the parking brake switch.

Did you complete the replacement?

--

System OK

--

11

Connect the parking brake switch.

Is the vehicle equipped with ABS?

--

Go to Step 12

Go to Step 14

12

  1. Turn the ignition OFF.
  2. Disconnect the electronic brake control module (EBCM) connector.
  3. Turn the ignition ON.

Is the lamp ON?

--

Go to Step 14

Go to Step 13

13

Replace the EBCM.

Did you complete the replacement?

--

System OK

--

14
  1. Turn the ignition OFF.
  2. Connect the EBCM connector.
  3. Check for a short to ground in the wiring between the instrument cluster terminal A19 (B15) and the brake fluid level switch.

Did you find the condition?

--

Go to Step 17

Go to Step 15

15

Check for a short to ground in the wiring between the instrument cluster terminal A19 (B15) and the parking brake switch.

Did you find the condition?

--

Go to Step 17

Go to Step 16

16

Check for a short to ground in the wiring between the instrument cluster terminal A19 (B15) and the EBCM connector terminal 21.

Did you find the condition?

--

Go to Step 17

Go to Step 18

17

Repair the wiring as needed.

Did you complete the repair?

--

System OK

--

18

Check the brake lamp after doing each of the following functions:

    • Apply the parking brake.
    • Remove the cap from the brake fluid reservoir.
    • On vehicles equipped with ABS, command the lamp ON using a scan tool.

Does the brake warning lamp operate for all of these conditions?

--

System OK

Go to Step 19

19

When the operations listed in step 18 were performed, the brake warning lamp did not function.

Did the brake warning lamp fail to light for all of the operations listed in step 18?

--

Go to Step 20

Go to Step 27

20
  1. Turn the ignition OFF.
  2. Inspect the kick panel fuse F4.

Is the fuse OK?

--

Go to Step 22

Go to Step 21

21

Replace the fuse.

Did you complete the replacement?

--

System OK

--

22

Inspect the brake warning lamp bulb.

Is the bulb OK?

--

Go to Step 24

Go to Step 23

23

Replace the bulb.

Did you complete the replacement?

--

System OK

--

24

  1. Disconnect the instrument cluster connector.
  2. Turn the ignition ON.
  3. Measure the voltage at the instrument cluster connector terminal A19 (B15).

Does the voltage measure within the specified range?

11-14 V

Go to Step 25

Go to Step 26

25
  1. Turn the ignition OFF.
  2. Repair the open in the instrument cluster.

Did you complete the repair?

--

System OK

--

26
  1. Turn the ignition OFF.
  2. Repair the open in the wiring between the instrument cluster connector terminal A19 (B15) and the ignition switch.

Did you complete the repair?

--

System OK

--

27

Apply the parking brake again.

Does the parking brake warning lamp operate with the parking brake applied?

--

Go to Step 28

Go to Step 30

28

Remove the brake fluid reservoir cap.

Does the parking brake warning lamp operate with the cap from the brake fluid reservoir removed?

--

Go to Step 29

Go to Step 32

29

Check for an open between the instrument cluster connector terminal A1 and the EBCM connector terminal 21.

Did you find the condition?

--

Go to Step 17

Go to Step 13

30

  1. Turn the ignition ON.
  2. Disconnect the parking brake switch.
  3. Jumper the parking brake switch connector terminal to ground.

Is the lamp ON?

--

Go to Step 10

Go to Step 31

31
  1. Turn the ignition OFF.
  2. Repair the open in the wire between the instrument cluster connector terminal A1 and the parking brake switch connector terminal.

Did you complete the repair?

--

System OK

--

32

  1. Disconnect the brake fluid level switch.
  2. Turn the ignition ON.
  3. Jumper the brake fluid level switch connector terminals.

Is the lamp ON?

--

Go to Step 8

Go to Step 33

33
  1. Turn the ignition OFF.
  2. Connect a test light between battery positive and the BRN/WHT wire terminal of the brake fluid level switch.

Is the test light ON?

--

Go to Step 34

Go to Step 35

34

Repair the open in the wiring between ground and the brake fluid level switch.

Did you complete the repair?

--

System OK

--

35

Repair the open in the wiring between the instrument cluster connector terminal A1 and the brake fluid level switch.

Did you complete the repair?

--

System OK

--