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
Items 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
Diagnostic System Check - Charging System
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
Vehicle Lifting Caution
in Cautions
and Notices.
- Turn the ignition switch to the OFF position.
- Connect the J 29532
according to the manufacturer's instructions.
- Turn the ignition switch to the ON position, engine OFF.
- Connect a scan tool and establish communication with the ABS system.
- 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 the J 29532
at 35 psi, and all the bleeder screws in the closed position, select
the Automated Bleed Procedure on the scan tool and follow the instructions.
- The first part of the automated bleed procedure will cycle the
pump and the 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 the 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 the J 29532
and then disconnect the 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.
- 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.