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Brake Hydraulic and Assist System Diagnosis (Two-mode Hybrid)

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
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DEFINITION: This diagnostic table is designed to diagnose ONLY the components of the brake HYDRAULIC and ASSIST systems in order to determine if the HYDRAULIC and ASSIST systems are operating properly. You will be directed by the appropriate Symptom table to go to other brake system diagnostic tables as appropriate.
1 Were you sent here from a Brake Symptom table or from an electrical diagnostic procedure? Go to Step 2  Go to Symptoms - Hydraulic Brakes 
2
  1. Inspect the brake fluid for the following conditions, indicating brake fluid contamination:
    • Fluid separation, indicating two types of fluid are present
      • Swirled appearance - oil-based substance
      • Layered appearance - silicone-based substance
    • Fluid discoloration
      • Cloudy appearance - moisture
      • Dark appearance/suspended particles in fluid - dirt, rust, corrosion, brake dust
  2. Inspect the master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating fluid contamination.
Do any of the above fluid contamination conditions exist?		 Go to Step 3  Go to Step 4 
3
  1. Flush the hydraulic brake system and repair or replace components as directed based upon the type of fluid contamination present. Refer to Hydraulic Brake System Flushing .
  2. Pressure bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual)  or Hydraulic Brake System Bleeding (Pressure) .
  3. Perform the Antilock Brake System Automated Bleed Procedure .
Did you complete the operation and any required repairs and/or replacements?		 Go to Step 4  -
4
  1. Inspect the following hydraulic brake system components for external fluid leaks:
    • Hydraulic brake hoses
    • Hydraulic brake pipes
    • Brake master cylinder reservoir to brake pressure modulator valve (BPMV) feed and return hoses
    • Brake calipers
    • Brake master cylinder
    • BPMV
  2. Inspect the hydraulic brake pipes, master cylinder reservoir hoses, and flexible brake hoses for signs of a fluid restriction, such as being bent, kinked, pinched, or damaged. Refer to Brake Pipe and Hose Inspection .
  3. Repair or replace any of the hydraulic components found to be leaking brake fluid.
  4. Replace any of the hydraulic brake pipes, master cylinder reservoir hoses, and/or flexible brake hoses found to be bent, kinked, pinched, or damaged.

    Refer to the appropriate procedures:

Did you complete the inspections and any necessary repairs or replacements?		 Go to Step 5  -
5 Perform the system deactivation and vehicle preparation steps:
NOTE: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see 1 pedal apply with the engine running, followed by a proper shutdown without applying the brake pedal.
  1. Start the engine and allow to idle.
  2. Apply and release the brake pedal.
  3. Place the transmission in PARK.
    4. NOTE: The ignition must be OFF, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1-3 minutes.
  4. Turn the ignition OFF, without pausing at ACCESSORY, and without applying the brake pedal.

    Remove the ignition key.

  5. Wait approximately 1-3 minutes until the brake modulator and HPA pressure relief is complete.
  6. Inspect and adjust the brake fluid level in the brake master cylinder reservoir. Refer to Master Cylinder Reservoir Filling (Without RPO HP5)  or Master Cylinder Reservoir Filling (With RPO HP5) .
  7. Connect a battery charger to the 12V battery. Refer to Battery Charging .
  8. Install a scan tool to the vehicle.
    9. NOTE: The ignition must remain ON, engine OFF during the remainder of this diagnostic procedure, unless otherwise instructed.
  9. Turn the ignition ON, engine OFF.
  10. Ensure the scan tool is communicating with the vehicle.

Did you complete the system deactivation and vehicle preparation steps?		 Go to Step 6  -
6 Have you already performed the brake sensor performance data checks as part of an electrical DTC diagnostic procedure? Go to Step 8  Go to Step 7 
7 Perform the brake sensor performance data check procedure.
  1. Start the engine and allow it to idle.
  2. Place the transmission in PARK.
    3. NOTE: Do not depress the brake pedal during the EBCM relearn.
  3. Using the scan tool, perform the EBCM relearn. Do not depress the brake pedal.
    1. Select Diagnostics.
    2. Select the appropriate vehicle information.
    3. Select Chassis.
    4. Select EBCM.
    5. Select Module Setup.
    6. Select EBCM Relearn and follow scan tool instructions.
    4. NOTE: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see 1 pedal apply with the engine running, followed by a proper shutdown without applying the brake pedal.
  4. Allow the engine to run at idle.
  5. Apply and release the brake pedal.
    6. NOTE: The ignition must be OFF, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1-3 minutes.
  6. Turn the ignition OFF, without pausing at ACCESSORY, and without applying the brake pedal.

    Remove the ignition key.

  7. Wait 3 minutes to ensure the brake modulator and HPA pressure relief is complete.
    8. NOTE: The ignition must remain ON, engine OFF during this entire procedure.
  8. Turn the ignition ON, engine OFF, and do not apply the brake pedal.
  9. Using the scan tool, select Data Display for the EBCM, scroll through the Data list, select and accept the following:
    • Master Cylinder Pressure Sensor
    • Rear Brake Pressure Sensor
    • Brake Pressure Sensor
    • Accumulator Pressure Sensor
    • Brake Master Cylinder (BMC) Primary Piston Position Sensor 5V Reference
    • BMC Primary Piston Position Sensor A
    • BMC Primary Piston Position Sensor B
  10. Ignition ON, engine OFF, brakes not applied, verify the following sensor parameters are within the specified values:
    • Master Cylinder Pressure Sensor - Less than 100 kPa (15 psi)
    • Rear Brake Pressure Sensor - Less than 100 kPa (15 psi)
    • Brake Pressure Sensor - Less than 100 kPa (15 psi)
    • Accumulator Pressure Sensor - Less than 800 kPa (116 psi)
  11. If any of the sensor parameters on the scan tool are not within the specified ranges, replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement .
  12. With the ignition ON, engine OFF, verify the following sensor parameters are within the specified values:
    • BMC Primary Piston Position Sensor 5V Reference - Between 4.75V and 5.25V
    • BMC Primary Piston Position Sensor A - Less than 0.8V
    • BMC Primary Piston Position Sensor B - Greater than 4.2V
  13. If any of the sensor parameters on the scan tool are not within the specified ranges, see the DTC C0277 for further diagnostic information.

Did you complete the operations and any required repairs and/or replacements?		 Go to Step 8  -
8 Inspect for proper brake pedal travel. Refer to Brake Pedal Travel Measurement and Inspection (Without RPO HP5)  or Brake Pedal Travel Measurement and Inspection (With RPO HP5) .
Was the brake pedal travel within specification?		 Go to Step 10  Go to Step 9 
9
  1. Inspect for worn, missing, misaligned, bent or damaged brake pedal system components.
    • For the brake pedal pushrod component inspection, refer to Brake Pedal Pushrod Inspection  .
    • Inspect the brake pedal bushings for excessive wear and/or damage and inspect the brake pedal for a misaligned, bent and/or damaged condition.
  2. Replace the brake pedal system components that are worn, missing, misaligned, bent or damaged.
  3. Perform the entire Antilock Brake System Automated Bleed Procedure .
  4. Re-inspect for proper brake pedal travel. Refer to Brake Pedal Travel Measurement and Inspection (Without RPO HP5)  or Brake Pedal Travel Measurement and Inspection (With RPO HP5) .
Is the brake pedal now within specification?		 Go to Step 10  Go to Step 20 
10 Perform the brake master cylinder (BMC) primary circuit test:
    NOTE: The ignition must remain ON, engine OFF during this entire procedure.
  1. Ensure the switch is ON, engine OFF.
  2. Using the scan tool, select Data Display for the EBCM, scroll through the Data list, select and accept the following:
    • Master Cylinder Pressure Sensor
    • Brake Master Cylinder (BMC) Primary Piston Reference Position
  3. While observing the master cylinder pressure and the BMC primary piston position sensors on the scan tool data display, using moderate speed and moderate effort, apply and maintain the brake pedal to a force of 2500 kPa (363 psi).
  4. Wait for 10 seconds for the system to settle.
  5. While ensuring 2500 kPa (363 psi) of force is maintained, observe pedal operation for an additional 30 seconds.
NOTE: The brake pedal should remain firm and steady while maintaining the apply force during the observation period.

Did the brake pedal remain firm and steady during the observation period?		 Go to Step 11  Go to Step 20 
11 Ensure the brake corners are functioning properly:
    NOTE: The aid of an assistant will be necessary.
  1. Raise and support the vehicle. Allow the tire and wheel assemblies to rotate freely. Refer to Lifting and Jacking the Vehicle .
    2. NOTE: The ignition must remain ON, engine OFF during this entire procedure.
  2. Ensure the ignition is ON, engine OFF.
  3. Verify the park brake is released.
  4. Place the transmission in NEUTRAL.
  5. Continue observing the master cylinder pressure sensor on the scan tool data display.
  6. Using moderate speed and moderate effort, apply and maintain the brake pedal to a force of 2500-3000 kPa (363-435 psi).
  7. While maintaining the brake apply force, wait 10 seconds, then have an assistant attempt to rotate the rear wheels.
  8. If the rear wheels are locked, maintain that amount of apply force.
  9. If the rear wheels are not locked, increase the apply force just enough to lock the rear wheels. Maintain that amount of apply force.
  10. Have an assistant attempt to rotate the front wheels.
  11. Inspect any suspect brake corners for possible component hydraulic restriction and/or mechanical binding.
  12. Release the brake pedal and have an assistant rotate each of the wheels again to check for possible brake drag.
NOTE: None of the wheels should be able to be rotated during the brake apply. None of the wheels should exhibit drag after brake release.

Did the brake corners apply and release properly?		 Go to Step 14  Go to Step 12 
12 Determine if the brake caliper is restricting the flow of brake fluid and/or not operating properly.
  1. Remove the appropriate tire and wheel assembly. Refer to Tire and Wheel Removal and Installation .
  2. Inspect the hydraulic function of the brake caliper for proper operation. Refer to Hydraulic Brake Component Operation Visual Inspection .
  3. Open the suspected caliper bleeder valve.
  4. Using a large C-clamp or clamps, evenly compress the caliper piston or pistons. Observe for an unrestricted flow of brake fluid and for free movement of the caliper piston or pistons.
  5. Close the caliper bleeder valve.

Was the flow of brake fluid unrestricted and did the caliper piston or pistons move freely?		 Go to Step 13  Go to Step 19 
13 Determine if the brake hose is restricting the flow of brake fluid.
  1. Carefully inspect the flexible brake hose at the restricted location for signs of a fluid restriction, such as being bent, kinked, pinched, or damaged. Refer to Brake Pipe and Hose Inspection .
  2. Replace the brake hose if it is found to be damaged. Refer to the appropriate procedure:

Did you complete the inspection and any necessary replacement?		 Go to Step 14  -
14 Perform the BMC secondary circuit test.
    NOTE: The aid of an assistant will be necessary.
  1. Reinstall the tire and wheel assembly, if removed previously to verify brake corner function.
  2. With the vehicle still supported at a working height, allow the tire and wheel assemblies to rotate freely.
    3. NOTE: The ignition must remain ON, engine OFF during this entire procedure.
  3. Ensure the ignition is ON engine OFF and the transmission is in NEUTRAL.
  4. Continue observing the master cylinder pressure sensor on the scan tool data display.
  5. Using moderate speed and moderate effort, apply and maintain the brake pedal to a force of 2500-3000 kPa (363-435 psi).
  6. While maintaining the brake pedal apply force, wait 10 seconds, then have an assistant attempt to rotate the rear wheels.
  7. If the rear wheels are locked, maintain that amount of apply force.
  8. If the rear wheels are not locked, increase the apply force just enough to lock the rear wheels. Maintain that amount of apply force.
  9. Wait 20 seconds, then attempt to rotate the front wheels.
  10. Attempt to rotate the rear wheels again.
NOTE: None of the wheels should be able to be rotated during the brake apply.

Could any of the wheels be rotated during the brake apply?		 Go to Step 15  Go to Step 18 
15 Were either of the front wheels able to be rotated during the brake apply? Go to Step 20  Go to Step 16 
16 Perform the brake modulator motor, HPA, and fluid control solenoid test:
  1. Using the scan tool data display, scroll through the Data List, select and accept Accumulator Pressure Sensor.
  2. While observing the accumulator pressure sensor data, start the engine and allow it to idle to activate and pressurize the brake system.
  3. Observe the accumulator pressure sensor data for 40 seconds.
NOTE: The accumulator pressure sensor data should rise from 0 kPa (0 psi) to 17,000 kPa (2466 psi) within 40 seconds.

Did the brake modulator provide the specified amount of pressure within the allotted time period?		 Go to Step 18  Go to Step 17 
17
  1. Perform the entire brake system automated bleed procedure. Refer to Antilock Brake System Automated Bleed Procedure .
  2. Place the transmission PARK.
    3. NOTE: The ignition must be OFF, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1-3 minutes.
  3. Turn the ignition OFF, without pausing at ACCESSORY, and without applying the brake pedal.

    Remove the ignition key.

  4. Wait approximately 1-3 minutes until the brake modulator and HPA pressure relief is complete.
  5. Again perform the brake modulator motor, HPA, and fluid control solenoid test:
    1. Using the scan tool data display, scroll through the Data List, select and accept Accumulator Pressure Sensor.
    2. While observing the accumulator pressure sensor data, start the engine and allow it to idle to activate and pressurize the brake system.
    3. Observe the accumulator pressure sensor data for 40 seconds.
      NOTE: The accumulator pressure sensor should rise from 0 kPa (0 psi) to 17,000 kPa (2466 psi) within 40 seconds.
Did the brake modulator provide the specified amount of pressure within the allotted time period?		 Go to Step 18  Go to Step 21 
18 Perform the brake pedal simulator test:
  1. Start the engine and allow to idle to activate and pressurize the brake system.
  2. Continue observing the master cylinder pressure and the BMC primary piston position sensors on the scan tool data display.
  3. Using moderate speed and moderate effort, apply and maintain the brake pedal to a force of 2500 kPa (363 psi).
  4. Observe both pedal operation and master cylinder pressure for a period of 20 seconds.
NOTE: The brake pedal should remain firm and steady and master cylinder pressure should remain constant.

Did the brake pedal remain firm and steady, and did the master cylinder pressure remain constant?		 Go to Step 22  Go to Step 21 
19 Repair or replace any brake caliper that was not operating properly. Refer to the appropriate procedure:
Did the brake pedal remain firm and steady, and did the master cylinder pressure remain constant?		 Go to Step 22  -
20
  1. Replace the brake master cylinder. Refer to Master Cylinder Replacement (Without RPO HP5)  or Master Cylinder Replacement (With RPO HP5) .
  2. Pressure bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual)  or Hydraulic Brake System Bleeding (Pressure) .
  3. Perform the entire brake system automated bleed procedure. Refer to Antilock Brake System Automated Bleed Procedure .
Did you complete the replacement and repair procedures?		 Go to Step 22  -
21
  1. Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement .
  2. Pressure bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual)  or Hydraulic Brake System Bleeding (Pressure) .
  3. Perform the entire brake system automated bleed procedure. Refer to Antilock Brake System Automated Bleed Procedure .
Did you complete the operation?		 Go to Step 22  -
22 Install or connect any components that were removed or disconnected during diagnosis.
Did you complete the operation?		 Brake Hydraulic and Assist System OK
Return to Symptom Table		 -
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