GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Savana 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Combination Valve Circuit

Step

Action

Value(s)

Yes

No

1

Was the Brake Warning System Check performed?

--

Go to Step 4

Go to Brake Warning System Check

2

  1. Disconnect the 2-way combination valve harness connector from the 4WAL Electro-Hydraulic Control Unit (EHCU).
  2. Connect terminal A of the 2-way combination valve harness connector to ground by using a jumper wire.
  3. Turn the ignition switch to the RUN position.

Does the BRAKE warning lamp turn on?

--

Go to Step 5

Go to Step 3

3

Check for an open BRAKE warning lamp.

Is the BRAKE warning lamp open?

--

Go to Step 10

Go to Step 4

4

Check for an open condition in the BRAKE warning lamp wiring circuit.

Is the wiring check complete?

--

Go to Step 5

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5
  1. Attach a hose to the rear bleeder screw.
  2. Immerse the other end of the hose in a container partially filled with brake fluid.
  3. Make sure that the brake fluid level in the master cylinder reservoir is full.
  4. Turn the ignition switch to the RUN position.
  5. Depress the brake pedal and hold at moderate pressure.
  6. Open the rear bleeder screw.

Does the BRAKE warning lamp turn on?

--

Go to Step 6

Go to Step 9

6
  1. Close the rear bleeder screw.
  2. Release the brake pedal.
  3. Apply moderate pressure to the brake pedal.

Does the BRAKE warning lamp turn on?

--

Go to Brake Warning System Check

Go to Step 7

7
  1. Attach a hose to the front bleeder screw.
  2. Immerse the other end of the hose in a container partially filled brake fluid.
  3. Make sure the brake fluid level in the master cylinder is correct.
  4. Depress the brake pedal and hold at moderate pressure.
  5. Open the front bleeder screw.

Does the BRAKE warning lamp turn on?

--

Go to Step 8

Go to Step 9

8
  1. Close the front bleeder screw.
  2. Release the brake pedal.
  3. Apply moderate pressure to the brake pedal.

Does the BRAKE warning lamp turn off?

--

Go to Brake Warning System Check

Go to Step 9

9

Replace combination valve. Refer to Combination Valve Replacement in Hydraulic Brakes.

Is the repair complete?

--

Go to Brake Warning System Check

--

10

Replace the BRAKE warning lamp.

Is the repair complete?

--

Go to Brake Warning System Check

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