Buick Enclave: Specifications, Diagnostic Information and Procedures
SPECIFICATIONS
FASTENER TIGHTENING SPECIFICATIONS
Fastener Tightening Specifications
BRAKE SYSTEM SPECIFICATIONS
Brake System Specifications
SCHEMATIC WIRING DIAGRAMS
HYDRAULIC BRAKE WIRING SCHEMATICS
Hydraulic Brake System
Fig. 1: Hydraulic Brake System Wiring Schematics
DIAGNOSTIC INFORMATION AND PROCEDURES
DIAGNOSTIC CODE INDEX
DTC C0267: LOW BRAKE FLUID INDICATED
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC C0267 00
- Low Brake Fluid Indicated
Diagnostic Fault Information
Circuit/System Description
The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the instrument panel cluster (IPC) sees the brake fluid level switch input closed, it turns ON the Red Brake Warning indicator and sends a serial data message to the electronic brake control module (EBCM) that the brake fluid level is low.
Conditions for Running the DTC
Ignition ON.
Conditions for Setting the DTC
- Low brake fluid is detected.
- A short to ground exists on the signal circuit.
Action Taken When the DTC Sets
- The EBCM disables the antilock brake system (ABS)/traction control system (TCS) dynamic rear proportion (DRP) and vehicle stability enhancement system (VSES).
- A DIC message and/or a warning indicator may be displayed.
Conditions for Clearing the DTC
- The condition for the DTC is no longer present.
- The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Reference Information
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
Description and Operation
Brake Warning System Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Inspect for proper brake fluid level, the fluid level should be at or above the proper level.
- If low, refer to Brake Fluid Loss.
2. Ignition ON, observe the scan tool IPC Brake Fluid parameter. The reading should be OK.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Test for less than 10 ohm between the ground circuit terminal A and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool IPC Brake Fluid parameter is Ok.
- If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the IPC.
4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool IPC Brake Fluid parameter is Low.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.
5. If all circuits test normal, test or replace the brake fluid level switch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Brake Fluid Level Indicator Switch Replacement
- Control Module References for IPC replacement, setup and programming
DTC C0299: BRAKE BOOSTER PRESSURE SENSOR PERFORMANCE PLAUSIBILITY FAILURE
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC C0299 5A
- Brake Booster Pressure Sensor Performance Plausibility Failure
Circuit/System Description
The power brake booster vacuum sensor monitors the vacuum level in the power brake booster. When the electronic brake control module (EBCM) detects the vacuum level is low a DTC is set.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
Low or no vacuum is detected in the power brake booster after start-up.
Conditions for Clearing the DTC
- The condition for the DTC is no longer present.
- The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Reference Information
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
Description and Operation
Brake Assist System Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Verify that a vacuum leak is not present, refer to Brake Assist System Diagnosis.
2. Verify that DTC C1100 is not set.
- If DTC is set, refer to DTC C1100.
DTC C1100: BASE BRAKE SYSTEM PRESSURE CIRCUIT
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC C1100 00
- Base Brake System Pressure Circuit
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) provides a 5-volt reference to the brake booster vacuum sensor.
The brake booster vacuum sensor converts the change in vacuum levels in the brake booster into a signal voltage ranging from 0.13-3.30 volts and is monitored by EBCM.
Conditions for Running the DTC
Ignition ON.
Conditions for Setting the DTC
The brake booster sensor signal voltage is not within 0.13-3.30 volts for more than 1 second.
Conditions for Clearing the DTC
- The condition for the DTC is no longer present.
- The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Reference Information
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
Description and Operation
Brake Assist System Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the brake booster vacuum sensor.
2. Wait for 60 seconds, test for less than 11 ohms between the low reference circuit terminal 2 and ground.
- If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground.
- If less than the specified range, test the 5 V reference circuit for an open/high resistance. If the circuit tests normal, replace the replace the EBCM.
- If greater than the specified range, test the 5 V reference circuit for a short to B+. If the circuit tests normal, replace the EBCM.
4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and the signal circuit terminal 1.
- If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.
- If greater than the specified range, test the signal circuit for a short to B+. If the circuit tests normal, replace the EBCM.
5. Ignition OFF, disconnect the harness connector at the EBCM.
6. Test for infinite resistance between the signal circuit terminal 1 and ground.
- If not the specified value, test the signal circuit for a short to ground.
7. If all circuits test normal, test or replace the brake booster vacuum sensor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Power Brake Booster Vacuum Sensor Replacement
- Control Module References for EBCM replacement, setup and programming
DTC P258A-P258D: VACUUM PUMP/VACUUM PUMP RELAY
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P258A
- Vacuum Pump Relay Control Circuit
DTC P258B
- Vacuum Pump Performance
DTC P258C
- Vacuum Pump Relay Control Circuit Low Voltage
DTC P258D
- Vacuum Pump Relay Control Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The engine control module (ECM) monitors the control circuit of the brake booster pump relay. The ECM supplies ground through the pump relay control circuit which then supplies B+ voltage to actuate the brake booster pump. B+ voltage is supplied at all times to the coil side of the pump relay.
Conditions for Running the DTC
P258A, P258C, P258D
Ignition ON.
P258B
- Engine Running
- Vacuum pump is activated for greater than 1.6 seconds.
Conditions for Setting the DTC
P258A, P258C
The ECM detects an open/high resistance on the relay coil control circuit.
P258B
The ECM detects an excessive difference in vacuum levels between the power brake booster and the manifold absolute pressure (MAP).
P258D
The ECM detects a short to voltage on the relay control circuit.
Action Taken When the DTC Sets
DTC P258A, P258B, P258C, P258D are Type B DTCs.
Conditions for Clearing the DTC
DTC P258A, P258B, P258C, P258D are Type B DTCs.
Reference Information
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
Description and Operation
Brake Assist System Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Verify that a vacuum leak is not present, refer to Brake System Vacuum Source Test 2. Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the vacuum relay and motor turns ON and OFF with each command.
Circuit/System Testing
1. Ignition OFF, disconnect the vacuum pump relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.
- Terminal 30
- Terminal 86
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or replace the relay.
4. Verify that a test lamp does not illuminate between the control circuit terminal 85 and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
5. Disconnect the harness connector at the vacuum pump.
6. Test for less than 2 ohms between the vacuum pump ground circuit terminal 2 and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the vacuum pump.
8. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
Verify the vacuum pump is activated.
- If the vacuum pump does not activate, test the control circuit for a short ground or an open/high resistance. If the circuit tests normal, test or replace the vacuum pump.
9. Ignition OFF, test for infinite resistance between the control circuit terminal 85 and ground.
- If less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
10. Disconnect the X1 harness connector at the ECM.
11. Test for less than 2 ohms between the control circuit terminal 85 at the relay cavity and terminal 18 at the ECM harness connector.
- If greater than the specified range, test the control circuit for an open/high resistance.
12. If all circuits test normal, replace the brake booster pump relay. If the DTC resets, replace the power brake booster vacuum pump.
Component Testing
1. Ignition OFF, disconnect the vacuum pump relay.
2. Test for 60-180 ohms between terminals 85 and 86.
- If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
- 30 and 85
- 30 and 87
- 30 and 86
- 86 and 87
- If not the specified value, replace the relay.
4. Install a 30A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground.
5. Test for less than 2 ohms between terminals 30 and 87.
- If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Relay Replacement (Within an Electrical Center) , Relay Replacement (Attached to Wire Harness)
- Power Brake Booster Auxiliary Pump Replacement
- Control Module References for ECM replacement, setup and programming
SYMPTOMS - HYDRAULIC BRAKES
IMPORTANT: The following steps must be completed before using the symptom tables.
- Perform the Brake System Vehicle Road Test before using the hydraulic brake symptom tables in order to duplicate the customer's concern.
- Review the system operation in order to familiarize yourself with
the
system functions. Refer to the following:
- Brake Warning System Description and Operation
- Hydraulic Brake System Description and Operation
- Brake Assist System Description and Operation
- Hydraulic Brake Component Operation Visual Inspection
Visual/Physical Inspection
- Inspect for aftermarket devices which could affect the operation of the Hydraulic Brake System. Refer to Checking Aftermarket Accessories.
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
- Brake Warning Indicator Malfunction
- Brake Pulsation
- Brake System Noise
- Braking Action Uneven - Pulls to One Side
- Braking Action Uneven - Front to Rear
- Brake Pedal Excessive Travel
- Brake Pedal Excessive Effort
- Brakes Drag
- Brake Fluid Loss
- Hydraulic Brake System Diagnosis
- Brake Assist System Diagnosis
BRAKE WARNING INDICATOR MALFUNCTION
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The instrument panel cluster (IPC) sees the brake fluid level switch input opens and illuminates the Red Brake Warning indicator. The body control module (BCM) sees the park brake switch input grounded, it sends a serial data message to the IPC requesting illumination of the Red Brake Warning indicator.
Reference Information
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
COMPONENT CONNECTOR END VIEWS - INDEX
Description and Operation
Brake Warning System Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Verify the park brake is released and the brake fluid is at or above the proper level.
- If low, refer to Brake Fluid Loss.
2. Command the IPC display test with a scan tool, the warning indicator should turn ON.
- If the red brake warning indicator does not illuminate, replace the IPC.
3. Ignition ON, observe the scan tool BCM Park Brake Switch parameter while applying and releasing the park brake. The parameter should cycle between Applied and Release.
- If the parameter does not cycle between the specified values, refer to Circuit/System Testing - Park Brake Switch Malfunction.
4. Observe the scan tool IPC Brake Fluid parameter. The reading should be OK.
- If not the specified value, refer to Circuit/System Testing - Brake Fluid Level Switch Malfunction.
Circuit/System Testing
Park Brake Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the park brake switch.
2. Ignition ON, verify the scan tool BCM Park Brake Switch parameter is Released.
- If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
3. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool BCM Park Brake Switch parameter is Applied.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance.
4. If all circuits test normal, test or replace the park brake switch.
Brake Fluid Level Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Test for less than 1 ohm between the ground circuit terminal A and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool IPC Brake Fluid parameter is Ok.
- If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the IPC.
4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool IPC Brake Fluid parameter is Low.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.
5. If all circuits test normal, test or replace the brake fluid level switch.
Component Testing
Park Brake Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the park brake switch.
2. Test for infinite resistance between the signal terminal A and ground with the park brake released.
- If less than the specified value, replace the park brake switch.
3. Test for less than 1 ohm between the signal terminal A and ground with the park brake applied.
- If greater than the specified range, replace the park brake switch.
Brake Fluid Level Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Test for infinite resistance between the ground terminal A and the signal terminal B.
- If less than the specified value, replace the brake fluid level switch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Brake Fluid Level Indicator Switch Replacement
- Parking Brake Indicator Switch Replacement
- Control Module References for BCM and IPC replacement, setup and programming
BRAKE PULSATION
Brake Pulsation
BRAKE SYSTEM NOISE
Brake System Noise
BRAKING ACTION UNEVEN - PULLS TO ONE SIDE
Test Description
The numbers below refer to the step numbers on the diagnostic table.
4
Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.
5
Steering components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.
Braking Action Uneven - Pulls to One Side
BRAKING ACTION UNEVEN - FRONT TO REAR
Test Descriptions
The number below refers to the step number on the diagnostic table.
4
Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.
Braking Action Uneven - Front to Rear
BRAKE PEDAL EXCESSIVE TRAVEL
Brake Pedal Excessive Travel
BRAKE PEDAL EXCESSIVE EFFORT
Brake Pedal Excessive Effort
BRAKES DRAG
Brakes Drag
BRAKE SYSTEM SLOW RELEASE
Brake System Slow Release
BRAKE FLUID LOSS
Brake Fluid Loss
DISC BRAKE SYSTEM DIAGNOSIS
Test Description
The numbers below refer to the step numbers on the diagnostic table.
9
Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
10
Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
12
Disc brake rotor shields/backing plates that come in contact with disc brake rotors may cause brake system noise.
15
Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.
19
Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.
22
Disc brake rotor assembled lateral runout (LRO) that exceeds the maximum acceptable level can lead to thickness variation.
Disc Brake System Diagnosis
HYDRAULIC BRAKE SYSTEM DIAGNOSIS
Hydraulic Brake System Diagnosis
BRAKE ASSIST SYSTEM DIAGNOSIS
Brake Assist System Diagnosis
BRAKE SYSTEM VEHICLE ROAD TEST
Preliminary Inspections
1. Visually inspect easily accessible brake system components for obvious damage and/or leaks which may indicate that the vehicle should not be driven until further inspections have been completed.
2. Inspect the brake master cylinder reservoir fluid level and adjust only if necessary for brake system road testing. Refer to Master Cylinder Reservoir Filling.
3. Inspect the tire inflation pressures and adjust as necessary.
4. Inspect the tire tread patterns to ensure that they are the same or very similar, especially per axle.
5. Ensure that the vehicle is not loaded unevenly prior to brake system road testing.
Road Testing Procedure
WARNING: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control.
Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. Start the engine and allow it to idle.
2. Check to see if the brake system warning lamp remains illuminated.
3. If the brake system warning lamp remains illuminated, DO NOT proceed to test drive the vehicle until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes.
4. Select a smooth, dry, clean and level road or large lot that is as free of traffic and obstacles as possible for brake system low speed road testing.
5. With the transmission in PARK, lightly apply the brake pedal. Observe both the pedal feel and the pedal travel.
6. If the brake pedal apply felt spongy or the pedal travel was excessive, DO NOT drive the vehicle until it is repaired.
7. If the brake pedal apply did not feel spongy and the pedal travel was not excessive, proceed to step 8.
8. Release and apply the brakes.
9. While continuing to apply the brakes, shift the transmission into DRIVE, release the brakes and allow the engine to idle the vehicle away from the stopped position. Observe for a slow release of the brake system.
10. With the aid of an assistant to observe the vehicle's performance from outside of the vehicle, drive the vehicle at a low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to them, while you observe both the pedal effort and the pedal travel.
11. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.
12. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 13.
13. Drive the vehicle in the opposite direction, at the same low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to him.
14. Drive the vehicle at a low speed and shift the transmission into NEUTRAL without applying the brakes.
Observe for a rapid deceleration in vehicle speed, indicating possible brake drag.
15. Select a smooth, dry, clean and level road that is as free of heavy traffic as possible for brake system moderate speed road testing.
16. Drive the vehicle at a moderate speed. Observe for a pull and/or incorrect tracking of the vehicle without the brakes applied.
17. While continuing to drive the vehicle at a moderate speed, perform several light applies of the brakes.
Observe the pedal effort and the pedal travel, observe for brake system noise, pulsation and/or brake drag.
18. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.
19. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 20.
20. While continuing to drive the vehicle at a moderate speed, perform several moderate applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system pulsation and/or uneven braking action - either side to side or front to rear.
A small amount of vehicle front end dip is expected during a moderate apply of the brakes.
21. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.
BRAKE PEDAL TRAVEL MEASUREMENT AND INSPECTION
Special Tools
- J 28662 Brake Pedal Effort Gauge
1. With the ignition OFF and the brakes cool, apply the brakes 3-5 times or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
2. Install the J 28662 brake pedal effort gauge to the brake pedal.
3. Measure and record the distance (1) from the brake pedal to the rim of the steering wheel; note the points of measurement.
Fig. 2: Measuring Brake Pedal Travel
4. Apply and maintain the brakes with 445 N (100 lb) of force to the brake pedal, as indicated on the J 28662 brake pedal effort gauge.
5. While maintaining 445 N (100 lb) of force to the brake pedal, measure and record the distance (2) from the same point on the brake pedal to the same point on the rim of the steering wheel.
6. Release the brakes and repeat steps 4 and 5 to obtain a second measurement. After obtaining a second measurement, proceed to step 7.
7. Average the first and second measurements recorded during the two applies of the brakes.
8. Subtract the initial measurement, unapplied (1), from the averaged, applied measurement (2) to obtain the brake pedal travel distance.
Specification
- Maximum brake pedal travel (measured with the ignition OFF, brake booster power assist depleted and the brakes cool): 45 mm (1.77 in)
BRAKE SYSTEM VACUUM SOURCE TEST
1. Disconnect the engine vacuum hose from the vacuum brake booster check valve.
NOTE:
- Engine temperature, accessory load and elevation level will affect engine vacuum.
- Vacuum readings will decrease by approximately 2.7 kPa (0.8 in Hg) for every 305 m (1000 ft) of elevation above sea level.
2. Install a vacuum gauge to the engine vacuum hose.
3. Start the engine and allow the engine to idle until normal operating temperatures are reached.
4. With the vehicle in PARK, the engine idling and the air conditioning (A/C) system OFF, check to see if the engine vacuum reading is within the specified normal engine vacuum range.
Specification
- 47-68 kPa (14-20 in Hg)
5. Turn the ignition OFF.
6. If the engine vacuum reading was within the specified normal range, proceed to step 10.
7. If the engine vacuum reading was NOT within the specified normal range, inspect the engine vacuum hose for the following conditions:
- Loose connection to the engine
- Collapse, deformation or contamination
- Cracks, cuts, dry-rot
8. If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps 2- 4.
9. If none of these conditions were found with the engine vacuum hose, then there is an engine vacuum source problem, check the engine vacuum system.
10. Remove the vacuum brake booster check valve from the booster.
11. Install the check valve to the engine vacuum hose.
12. Install the vacuum gauge to the check valve.
13. Start the engine and allow the engine to idle in PARK with the A/C system OFF, until normal operating temperatures are reached.
14. Turn the ignition OFF.
15. Check to see if the engine vacuum reading is maintained within the specified normal engine vacuum range.
Specification
- 47-68 kPa (14-20 in Hg)
16. If the engine vacuum reading is maintained within the specified normal range, proceed to step 18.
17. If the engine vacuum reading is NOT maintained within the specified normal range, replace the brake booster check valve, then repeat steps 11-15.
18. Inspect the brake booster check valve grommet for the following conditions:
- Loose connection to the vacuum brake booster
- Deformation or contamination
- Cracks, cuts, dry-rot
19. If any of these conditions were found with the check valve grommet, replace the grommet.
BRAKE SYSTEM EXTERNAL LEAK INSPECTION
WARNING: Refer to Brake Fluid Irritant Warning.
CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.
1. In order to inspect for external brake fluid leaks, first check the fluid level in the master cylinder.
While a slight brake fluid level drop can be considered a normal condition due to brake lining wear, a very low level may indicate a brake fluid leak in the hydraulic system.
2. If the fluid level is abnormally low, adjust the brake fluid level. Refer to Master Cylinder Reservoir Filling.
3. Start the engine and allow it to idle.
4. Apply constant, moderate foot pressure to the brake pedal.
If the brake pedal gradually falls away while under foot pressure, there may be a brake fluid leak.
5. Turn OFF the ignition.
6. Visually inspect the following brake system components for brake fluid leaks, excessive corrosion and damage. Give particular attention to all brake pipe and flexible hose connections to ensure that there are not any slight brake fluid leaks - even though the brake pedal may feel firm and hold steady:
- Master cylinder brake pipe fittings
- All brake pipe connections
- Brake pipes
- Brake hoses and connections
- Brake calipers and/or wheel cylinders, if equipped
7. While slight dampness around the master cylinder reservoir can be considered acceptable, brake fluid leaking from any of the brake system components requires immediate attention. If any of these components exhibit signs of brake fluid leakage, repair or replace those components. After the repair or replacement, reinspect the hydraulic brake system to assure proper function.
BRAKE SYSTEM INTERNAL LEAK TEST
WARNING: Refer to Brake Fluid Irritant Warning.
CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.
1. Start the engine and allow it to idle.
2. Apply light, steady pressure to the brake pedal. Observe both the brake pedal feel and travel.
3. Release the brakes and turn OFF the ignition.
4. If the brake pedal apply felt spongy, but the brake pedal travel was not excessive, perform the following steps:
- Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.
- Pressure bleed the brake system in order to purge any air that may be trapped in the system. Refer to Hydraulic Brake System Bleeding (Manual), Hydraulic Brake System Bleeding (Pressure).
5. If the brake pedal apply did not feel spongy, but the brake pedal travel was excessive, perform the following steps:
Fig. 3: Identifying Brake Master Cylinder (Cross Sectional View)
- Loosen the master cylinder-to-brake power booster mounting nuts.
- Carefully pull the master cylinder away from the brake power booster just enough to inspect the mounting surface of the master cylinder.
- Inspect the master cylinder mounting surface at the primary piston (2) for brake fluid leaks.
6. If the master cylinder exhibits any leakage around the primary piston (2), then the primary piston primary seal (4) and/or secondary seal (3) is leaking and the master cylinder requires overhaul or replacement.
7. If the master cylinder primary piston (2) does not exhibit any leakage, pressure bleed the brake system.
Refer to Hydraulic Brake System Bleeding (Manual), Hydraulic Brake System Bleeding (Pressure).
8. If the brake pedal apply did not feel spongy and the brake pedal travel was initially steady and not excessive, but then gradually fell, then the master cylinder requires overhaul or replacement due to an internal leak past the secondary piston (1) from the secondary piston primary seal (6) or secondary seal (5).
9. If the brake pedal apply did not feel spongy and the brake pedal travel was initially steady and not excessive, then fell slightly, then became steady again, then the brake pressure modulator valve (BPMV) may be leaking internally and may require replacement.
HYDRAULIC BRAKE COMPONENT OPERATION VISUAL INSPECTION
1. With the tire and wheel assemblies removed and the brake rotors retained by wheel lug nuts, visually inspect the caliper piston dust boot (2) sealing area to ensure that there are no brake fluid leaks.
Fig. 4: Identifying Brake Caliper/Pad Inspection Areas
WARNING: Refer to Brake Fluid Irritant Warning.
CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.
2. If any evidence of a brake fluid leak is present, the brake caliper requires overhaul or replacement.
3. While the brake system is at rest (4), observe the position of the caliper piston (1) in relation to the caliper housing.
4. Have an assistant apply and release the brake pedal several times while you observe the operation of the hydraulic brake caliper.
- Observe the caliper piston (1) for unrestricted and even movement during each apply of the brake system (5).
- Observe the caliper piston (1) for an unrestricted and even return motion during each release of the brake system (6).
5. If the caliper piston (1) did not exhibit unrestricted and even movement during brake system apply and/or release, the piston square seal (3) may be worn or damaged and the caliper may require overhaul or replacement.
BRAKE PIPE AND HOSE INSPECTION
WARNING: Refer to Brake Fluid Irritant Warning.
CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.
1. Visually inspect all of the brake pipes for the following conditions:
- Kinks, improper routing, missing or damaged retainers
- Leaking fittings, excessive corrosion
2. If any of the brake pipes exhibited any of the conditions listed, then the identified pipe or pipes, require replacement.
3. Ensure that the vehicle axles are properly supported at ride height in order to maintain the proper relationship of the flexible brake hoses to the chassis.
4. Visually inspect all of the flexible brake hoses for the following conditions:
Fig. 5: Identifying Flexible Brake Hose Failure Conditions
- Kinks (1), improper routing, twists, chafing, missing or damaged retainers
- Leaking connections, cracking, dry-rot, blisters, bulges
5. If any of the flexible brake hoses exhibited any of the conditions listed, then the identified flexible brake hose or hoses require replacement.
6. Squeeze the flexible brake hoses with firm finger pressure to check for soft spots (2), indicating an internal restriction. Check the entire length of each flexible brake hose.
7. If any of the flexible brake hoses were found to have soft spots (2), then the identified flexible brake hose or hoses require replacement.
BRAKE PEDAL PUSHROD INSPECTION
1. Disconnect the brake pedal pushrod (1) from the brake pedal.
Fig. 6: View of Brake Pedal Pushrod
2. Inspect the brake pedal pushrod eyelet bushing (2), if equipped, for cracks and/or excessive wear.
3. Reposition the pedal pushrod boot (3) toward the front of the vehicle to expose as much of the pedal pushrod (1) as possible.
4. Inspect the brake pedal pushrod (1) for straightness.
5. If the brake pedal pushrod eyelet bushing (2) exhibited cracks and/or excessive wear, then the bushing requires replacement.
6. If the brake pedal pushrod (1) is not straight, then the pushrod requires replacement.
7. Return the pedal pushrod boot (3) to its original position on the pedal pushrod (1).
8. Connect the brake pedal pushrod (1) to the brake pedal.
