GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 GMC C-Series Medium Duty Truck B7 🢒 Brakes 🢒 Hydraulic Brakes 🢒 AUX BRAKE Indicator and Alarm On with Engine Running

Step

Action

Value(s)

Yes

No

1
  1. Disconnect the multifunction alarm module connector.
  2. Connect a test lamp from CKT 39 (PNK) terminal A5 to CKT 1928 (LT BLU/BLK) terminal A1 at the multifunction alarm module.
  3. Start the engine and run the engine for 30 seconds.

Does the test lamp light?

--

Go to Step 2

Go to Step 4

2
  1. Disconnect the brake fluid flow switch connector with the engine running.
  2. Leave the test lamp connected as described in Step 1.

Does the test lamp light?

--

Go to Step 3

Go to Step 11

3

Repair the short to ground in CKT 1928 (LT BLU) between the following components:

    • The multifunction alarm module
    • The brake fluid flow switch
    • The hydraulic brake relay

Is the repair complete?

--

System OK

--

4
  1. Connect the test lamp between CKT 39 (PNK) and CKT 1740 (ORN) at the multifunction alarm module.
  2. Start the engine and run the engine.

Does the test lamp light?

--

Go to Step 9

Go to Step 5

5
  1. Turn the engine OFF.
  2. Disconnect the power brake booster motor connector.
  3. Install a fused jumper wire between CKT 150 (BLK) and CKT 1470 (RED) at the power brake booster motor connector.
  4. Keep the test lamp connected at the multifunction alarm module connector.
  5. Place the ignition switch in the RUN position.

Does the test lamp light?

--

Go to Step 6

Go to Step 7

6

Replace the power brake booster pump motor. Refer to Power Brake Booster Replacement .

Is the repair complete?

--

System OK

--

7

Use a J 39200 DMM from CKT 150 (BLK) at the power brake booster pump motor to ground.

Does the DMM indicate continuity?

--

Go to Step 8

Go to Step 12

8

Repair the open in CKT 1740 (ORN) or CKT 1470 (RED) between the power brake booster pump motor and the multifunction alarm module.

Is the repair complete?

--

System OK

--

9
  1. Connect a test lamp between CKT 150 (BLK) terminal A8 and CKT 847 (GRY) terminal B4 at the multifunction alarm module connector.
  2. Apply the service brakes.

Does the test lamp light?

--

Go to Step 10

Go to Exterior Lights System Check in Lighting Systems

10

Replace the multifunction alarm module. Refer to Multifunction Alarm Module Replacement in Instrument Panel, Gages and Console

Is the repair complete?

--

System OK

--

11

Replace the brake fluid flow switch. Refer to Fluid Flow Switch Replacement .

Is the repair complete?

--

System OK

--

12

Repair the open in CKT 150 (BLK) between the power brake booster motor and ground.

Is the repair correct?

--

System OK

--