Perform the automated ABS bleed procedure whenever one of the following conditions
occurs:
• | Manual bleeding at the wheel cylinders does not achieve the desired pedal
height or feel. |
• | You replace the Brake Pressure Modulator Valve (BPMV). |
• | Extreme loss of brake fluid has occurred. |
• | Air ingestion is suspected. |
If none of the above conditions applies, use standard bleed procedures. Refer
to Hydraulic Brake System Bleeding in hydraulic brakes.
This procedure uses a scan tool in order to cycle the system solenoid valves
and to run the pump motor in order to purge the air from the secondary circuits.
These secondary circuits are normally closed, and are only opened during system
initialization at vehicle start up and during ABS operation. The automated bleed
procedure opens these secondary circuits and allows any air trapped inside the
BPMV to flow out toward the wheel cylinders or the calipers where the air can
be purged out of the system.
Automated Bleed Procedure
Tools Required
• | J 29532 pressure
bleeder with the proper master cylinder adapter |
• | Delco Supreme 11 or equivalent Dot 3 brake fluid from a
clean, sealed container |
• | An unbreakable plastic bleeder bottle equipped with a hose to recover
fluid at the wheels |
• | An assistant, if needed |
• | The suitable safety attire, including safety glasses |
Preliminary Inspection
- Inspect the battery for full charge, repair the battery and charging
system as necessary. Refer to
Battery Charge Low or Completely Discharged
in
Engine Electrical.
- Connect a scan tool to the DLC connector and select Current and History
DTCs. Repair any DTCs prior to performing the ABS bleed procedure.
- Inspect for visual damage and leaks, repair as needed.
Preliminary Setup
- Raise and support the vehicle on a suitable support. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Turn the ignition switch to the OFF position.
- Connect the J 29532
according
to the manufacturer's instructions.
- Turn the ignition switch to ON position, engine OFF.
- Connect a scan tool and establish communications with the ABS system.
- Remove all 4 tires, if necessary.
- Pressurize the bleeding tool to 35 psi.
Performing the Automated Bleed Procedure
Notice: The Auto Bleed Procedure may be terminated at any time during the process
by pressing the EXIT button. No further Scan Tool prompts pertaining to the
Auto Bleed procedure will be given. After exiting the bleed procedure, relieve
bleed pressure and disconnect bleed equipment per manufacturers instructions.
Failure to properly relieve pressure may result in spilled brake fluid causing
damage to components and painted surfaces.
- With J 29532
at 35 psi, and all bleeder screws in closed position, select Automated
Bleed Procedure on the scan tool and follow the instructions.
- The first part of the automated bleed procedure will cycle the pump and
front release valves for 1 minute. After the cycling has stopped the scan
tool will enter a cool down mode and display a 3-minute timer. The auto bleed
will not continue until this timer expires. You cannot override this timer.
- The scan tool will request the technician to open one of the bleeder
valves. The scan tool will then cycle this valve and the pump motor for 1 minute.
- The scan tool repeats step 3 for the remaining bleeder valves.
- With J 29532
still
attached to the vehicle and maintaining 35 psi, the scan tool will instruct
the technician to independently open each bleeder screw for approximately 20 seconds.
This should allow any remaining air to be purged from the brake pipes.
- When the automated bleed procedure is completed, the scan tool will display
the appropriate message.
- Remove pressure from J 29532
and then disconnect J 29532
from the vehicle.
- Depress the brake pedal in order to gauge the pedal height and feel.
- Repeat steps 1-8 until the pedal is acceptable.
- Remove the scan tool from the DLC.
- Install the tire and wheels assemblies, if removed.
- Lower the vehicle.
- Inspect the brake fluid level in the master cylinder.
- Road test the vehicle while verifying that the brake pedal remains high
and firm.