Antilock Brake System Automated Bleed Procedure

Antilock Brake System Automated Bleed Procedure (Non-Hybrid Vehicles)
Caution: Refer to Brake Fluid Irritant Caution (Brake Fluid Irritant Caution).

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice (Brake Fluid Effects on Paint and Electrical Components Notice).


Important:
* Before performing the ABS Automated Bleed Procedure, first perform a manual or pressure bleed of the base hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Pressure) (Service and Repair)Hydraulic Brake System Bleeding (Manual) (Service and Repair).

* The automated bleed procedure must be performed when a new brake pressure modulator valve (BPMV) is installed, because the secondary circuits of the new BPMV are not prefilled with brake fluid.

* The automated bleed procedure is recommended when one of the following conditions exist:


* Base brake system bleeding does not achieve the desired pedal height or feel

* Extreme loss of brake fluid has occurred

* Air ingestion is suspected in the secondary circuits of the brake modulator assembly





The ABS Automated Bleed Procedure uses a scan tool to cycle the system solenoid valves and run the pump in order to purge any air from the secondary circuits. These 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 in these circuits to flow out away from the brake modulator assembly, which is then forced out at the brake corners by the pressure bleeder.


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.

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (Service Intervals).
2. Remove the tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation (Service and Repair).
3. Inspect the brake system for leaks and visual damage. Refer to Symptoms - Hydraulic Brakes (Symptoms - Hydraulic Brakes). Repair or replace components as needed.
4. Lower the vehicle.
5. Prepare the brake bleeding equipment and the vehicle for a pressure bleed of the base hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Pressure) (Service and Repair)Hydraulic Brake System Bleeding (Manual) (Service and Repair).
6. Inspect the battery state of charge. Refer to Battery Inspection/Test (Battery Inspection/Test).
7. Install a scan tool.
8. Turn the ignition ON, with the engine OFF.
9. With the scan tool, perform the following steps:

1. Select Diagnostics
2. Select the appropriate vehicle information
3. Select Chassis
4. Select Electronic Brake Control Module (EBCM)
5. Select Special Functions
6. Select Automated Bleed

10. With an assistant ready, raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (Service Intervals).

Important: Follow the steps listed below instead of the steps given on the scan tool.


11. Perform the automated bleed procedure as listed below. Do not follow the instructions as shown on the scan tool unless instructed to do so during the following steps.


Important:
* Do not release the brake pedal when the scan tool instructs. Only release the brake pedal while following the procedure below.

* Bleed each corner as follows:


- Left front

- Right front

- Right rear

- Left rear




1. Following the scan tool instruction, press and hold the brake pedal using moderate pressure.
- After the ABS modulator has finished cycling, continue to maintain moderate pressure on the brake pedal. Do not release the brake pedal as instructed on the scan tool.
- While maintaining moderate pressure on the brake pedal, have an assistant open the left front bleeder valve.
- Allow the bleeder to remain open for 60 seconds while maintaining moderate pressure on the brake pedal.
- After 60 seconds, have the assistant close the bleeder valve.
- Slowly release the brake pedal.
- Using the scan tool, again select Automated Bleed from the Special Functions menu.
- Wait 15 seconds, press and hold the brake pedal using moderate pressure and repeat Step 11 completely for the next bleeder valve in clockwise sequence.

12. If the automated bleed procedure is aborted, a malfunction exists. If a DTC is detected, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) to diagnose the DTC.
13. After completion of the automated bleed procedure, press and hold the brake pedal to inspect for pedal firmness.
14. If the brake pedal feels spongy, repeat Step 11 completely.
15. Remove the scan tool.
16. Install the tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation (Service and Repair).
17. Lower the vehicle.
18. Adjust the brake fluid level. Refer to Master Cylinder Reservoir Filling (Master Cylinder Reservoir Filling).
19. Road test the vehicle while confirming the brake pedal remains high and firm.