GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Savana 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake Warning Alarm Inoperative

Circuit Description

The Brake Warning indicator illuminates and the power brake booster fluid flow alarm sounds when ground is applied to the brake warning indicator voltage 2 circuit.

Test Description

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

  1. This step tests for ground on the brake fluid level sensor signal circuit.

    2.

  2. This step tests the function of the brake fluid level sensor signal circuit and the P/B Booster Fluid Flow And Pressure Alarm Delay Module.

    3.

  3. This step tests for an open power brake booster fluid pressure alarm switch.

    4.

  4. The P/B Booster Fluid Flow And Pressure Alarm Delay Module may be damaged if the brake warning indicator supply voltage 2 circuit is shorted to voltage.

    5.

  5. This step tests the resistance value of the resistor wired in parallel with the power brake booster fluid flow alarm. The P/B Booster Fluid Flow And Pressure Alarm Delay Module may be damaged if this resistance is not within specification.

Step

Action

Yes

No

Schematic Reference: Brake Warning System Schematics

1

Did you review the Brake Warning System Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Hydraulic Brakes

2

Turn ON the ignition.

Does the power brake booster fluid flow alarm sound continuously?

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

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the P/B booster fluid flow and pressure alarm delay module.
  3. Connect a fused jumper wire between the brake warning indicator supply voltage 2 circuit and a good ground.
  4. Turn ON the ignition.

Does the power brake booster fluid flow alarm sound continuously?

Go to Step 4

Go to Step 13

4

Connect a test lamp between battery voltage and the brake fluid level sensor signal circuit at the P/B booster fluid flow and pressure alarm delay module harness connector.

Does the test lamp illuminate?

Go to Step 19

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Reconnect the P/B booster fluid flow and pressure alarm delay module.
  3. Disconnect the power brake booster fluid pressure alarm switch
  4. Connect a jumper wire between the brake fluid level sensor signal circuit and a good ground.
  5. Turn ON the ignition.

Does the power brake booster fluid flow alarm sound continuously?

Go to Step 6

Go to Step 7

6

Connect a jumper wire between the brake fluid level sensor signal circuit and the front windshield wiper switch high signal circuit at the power brake booster fluid pressure alarm switch harness connector.

Does the power brake booster fluid flow alarm sound continuously?

Go to Step 10

Go to Step 8

7

Test the brake fluid level sensor signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 19

8

Test the front windshield wiper switch high signal circuit and the ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 9

9

Inspect for poor connections at the power brake booster fluid flow alarm 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 21

Go to Step 12

10

Inspect for poor connections at the power brake booster fluid pressure alarm 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 21

Go to Step 11

11

Replace the power brake booster fluid pressure alarm switch.

Did you complete the replacement?

Go to Step 21

--

12

Replace the power brake booster fluid flow alarm switch.

Did you complete the replacement?

Go to Step 21

--

13

Test the ignition 3 voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 14

14

Test the brake warning indicator supply voltage 2 circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 15

15

  1. Remove the 10A BRAKE fuse.
  2. Disconnect the power brake booster fluid flow alarm harness connector.
  3. Use a DMM in order to measure the resistance between the ignition 3 voltage circuit and the brake warning indicator supply voltage 2 circuit at the power brake booster fluid flow alarm harness connector.

Does the resistance measure within the specified range?

Go to Step 17

Go to Step 16

16

Replace the inline resistor between the ignition 3 voltage circuit and the brake warning indicator supply voltage 2 circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the replacement?

Go to Step 21

--

17

Inspect for poor connections at the power brake booster fluid flow alarm. 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 21

Go to Step 18

18

Replace the power brake booster fluid flow alarm.

Did you complete the replacement?

Go to Step 21

--

19

Inspect for poor connections at the P/B booster fluid flow and pressure alarm delay module. 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 21

Go to Step 20

20

Replace the P/B booster fluid flow and pressure alarm delay module.

Did you complete the replacement?

Go to Step 21

--

21

Turn ON the ignition.

Does the power brake booster fluid flow alarm sound continuously?

System OK

Go to Step 3