Important: In most circumstances a base brake bleed is all that is required for
most component replacements (such as wheel cylinders, calipers, brake tubes,
and master cylinder) except for BPMV replacement.
The following automated ABS bleed procedure is required when one of
the following occur:
• | Manual bleeding at the wheel cylinders does not achieve the desired
pedal height or feel. |
• | BPMV (Brake Pressure Modulator Valve) replacement. |
• | Extreme loss of brake fluid has occurred. |
• | Air ingestion is suspected. |
If none of the above conditions apply use standard bleed procedures.
Refer to
Hydraulic Brake System Bleeding
in hydraulic brakes.
The auto bleed procedure is used on DBC 7 equipped vehicles. This procedure
uses a scan tool to cycle the system solenoid valves and run the pump in order
to purge the air from the secondary circuits. These secondary circuits are
normally closed off, 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 calipers where it can be purged
out of the system.
Automated Bleed Procedure
Items Required
• | A 35 psi 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 Data Link Connector (DLC) and select
current and history DTCs. Repair any DTCs prior to performing the ABS bleed
procedure.
- Inspect for visual damage and leaks and repair as needed.
Preliminary Setup
- Raise and vehicle on a suitable support. Refer to
Lifting and Jacking the Vehicle
in General Information.
- Turn the ignition switch to OFF position.
- Remove all four tires, if necessary.
- Connect the pressure bleeding tool according to the manufacturer's
instructions.
- Turn the ignition switch to RUN position, engine off.
- Connect a scan tool and establish communications with the ABS
system.
- Pressurize the bleeding tool to 30 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 the pressure bleeding tool at 30 to 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 one 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 expired, and cannot
be overridden.
- During the next step, the scan tool will request the technician
to open one of the bleeder screws. The scan tool will then cycle the respective
release valve and pump motor for 1 minute.
- The scan tool will repeat step 3 for the remaining bleeder screws.
- With the bleeder tool 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 lines.
- When the automated bleed procedure is completed the scan tool
will display the appropriate message.
- Remove pressure from the pressure bleeding tool and then disconnect
the tool from the vehicle.
- Depress the brake pedal to gauge pedal height and feel. Repeat
steps 1 through 8 until the pedal is acceptable.
- Remove the scan tool from the DLC connector.
- Install the tire and wheels assemblies, if they were removed.
- Lower the vehicle.
- Inspect the brake fluid level in master cylinder.
- Road test the vehicle while making sure the brake pedal remains
high and firm.
If vehicle is equipped with TCS the scan tool will cycle both the ABS
and TCS solenoids valves. This bleed procedure is the same as above.