Difference between revisions of "Anti-Lock Braking System"

Revision as of 00:54, 4 August 2008

ANTI-LOCK BRAKE SYSTEM

1994 Toyota Celica Anti-Lock Brake System

DESCRIPTION

Anti-Lock Brake System (ABS) consists of an ABS Electronic Control Unit (ECU), solenoid relay, motor relay, actuator and 4 speed sensors. See Fig. 1.

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An ABS indicator light is located on the instrument panel. This light comes on for 3 seconds as a bulb test when ignition is first turned on. A primary check is performed after each engine start, and initial vehicle speed exceeds 4 MPH. If brake pedal is pressed before vehicle exceeds 4 MPH, primary check will not occur until brake pedal is released.

OPERATION

Under normal driving conditions, ABS functions as a standard brake system. With detection of heel lock-up, short pedal pulsations occurring in rapid succession will be felt in brake pedal. Pedal pulsation will continue until there is no longer a need for ABS function.

CAUTION: See ANTI-LOCK BRAKE SAFETY PRECAUTIONS article in GENERAL INFORMATION.

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Fig. 1: Locating ABS Components (Courtesy of Toyota Motor Sales, U.S.A., Inc. )

BLEEDING BRAKE SYSTEM

CAUTION: Brake fluid will damage painted surfaces. If brake fluid gets on a painted surface, wipe off immediately and clean with alcohol. Use only DOT 3 brake fluid from a sealed container. Do not mix brake fluid with any other type.

Brake bleeding procedure is same procedure used to bleed non-ABS systems. If master cylinder was rebuilt or reservoir ran empty, bleed master cylinder first. Bleed remaining wheels, starting with brake having longest hydraulic line, working to brake with shortest hydraulic line.

ADJUSTMENTS

MASTER CYLINDER PUSH ROD

1) Install Adjusting Gauge (09737-00010) onto master cylinder, with master cylinder gasket in place. Lower gauge pin until it just touches master cylinder piston. See Fig. 2 (STEP 1). Invert gauge, then install onto power brake unit (STEP 2).

2) Measure clearance between brake unit push rod and head of adjusting gauge. Clearance should be zero. If clearance is not zero, adjust brake unit push rod length until push rod just touches head of gauge pin.

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Fig. 2: Adjusting Master Cylinder Push Rod (Courtesy of Toyota Motor Sales, U.S.A., Inc. )

BRAKE PEDAL HEIGHT

1) Measure brake pedal height from face of brake pedal pad to asphalt sheet under carpet. See Fig. 3. Brake pedal height should be 6.0-6.4" (152-162 mm). To adjust brake pedal height, remove instrument lower finish panel and air duct (if necessary). Unplug stoplight switch connector. Loosen stoplight switch and lock nut on brake pedal push rod.

2) Adjust pedal height by rotating push rod. After adjusting brake pedal height, tighten lock nut. Adjust stoplight switch. See STOPLIGHT SWITCH. Check and adjust brake pedal free play. See BRAKE PEDAL FREE PLAY.

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Fig. 3: Measuring Brake Pedal Height & Free Play (Courtesy of Toyota Motor Sales, U.S.A., Inc. )

BRAKE PEDAL FREE PLAY

1) Brake pedal free play is distance brake pedal travels (with engine stopped) before encountering resistance. To measure brake pedal free play, press brake pedal several times to exhaust vacuum from power brake unit. Press brake pedal and measure travel until initial resistance occurs.

2) Brake pedal free play should be .04-.24" (1-6 mm). If free play is not within specification, adjust by rotating push rod. See Fig. 3. After adjusting brake pedal free play, check brake pedal height. See BRAKE PEDAL HEIGHT.

BRAKE PEDAL RESERVE DISTANCE

Measure brake pedal reserve distance from face of brake pedal pad to asphalt sheet under carpet, with engine running and force of 110 lbs. (50 kg) applied to brake pedal. Minimum brake pedal reserve distance should be 3.35" (85 mm) for vehicles with 1.8L engine, or 3.54" (90.0 mm) for vehicles with 2.2L engine. If distance is less than specified, inspect brake system.

STOPLIGHT SWITCH

Stoplight switch is located above brake pedal. See Fig. 3. To adjust stoplight switch, loosen stoplight switch lock nuts and rotate stoplight switch until clearance between pedal stop and threaded end of switch is .02-.09" (0.5-2.3 mm). Tighten lock nut. Check stoplight operation.

PARKING BRAKE SHOES (DISC)

Raise and support vehicle. Remove wheels. Temporarily install lug nuts to hold brake rotor in place. Remove hole plug to gain access to adjuster. Turn adjuster to expand shoes until brake rotor locks. Back off adjuster 8 notches. Install hole plug.

PARKING BRAKE

NOTE: Service brake on rear drum brakes and parking brake shoe clearance on rear disc brakes must be adjusted before adjusting parking brake cable. Parking brake lever stroke should be 4-7 clicks with a pull force of 44 lbs. (20 kg). To adjust stroke, remove console box. Loosen parking brake cable lock nut. Rotate adjuster nut until parking brake lever travel is as specified. Tighten lock nut. Install console box.

TROUBLESHOOTING

ABS Does Not Operate

Verify that only normal code exists. SEE RETRIEVING CODES under DIAGNOSIS & TESTING. Check IG1 power source. See IG1 POWER SOURCE CIRCUIT under DIAGNOSIS & TESTING. See WIRING DIAGRAM. Check ABS actuator. See ACTUATOR CHECK under DIAGNOSIS & TESTING.

ABS Does Not Operate Efficiently

Verify that only normal code exists. SEE RETRIEVING CODES under DIAGNOSIS & TESTING. Check stoplight circuit. See WIRING DIAGRAM. Check ABS actuator. See ACTUATOR CHECK under DIAGNOSIS & TESTING.

ABS Warning Light Abnormal

See ABS WARNING LIGHT CIRCUIT under DIAGNOSIS & TESTING.

Cannot Retrieve Codes

Check ABS warning light circuit. See ABS WARNING LIGHT CIRCUIT under DIAGNOSIS & TESTING. Check Tc terminal circuit. See Tc TERMINAL CIRCUIT under DIAGNOSIS & TESTING.

Cannot Perform Sensor Signal Check

Check Ts terminal circuit. See Ts TERMINAL CIRCUIT under DIAGNOSIS & TESTING.

DIAGNOSIS & TESTING

NOTE: DO NOT start engine when retrieving diagnostic codes.

RETRIEVING CODES

1)Ensure battery voltage is about 12 volts. Turn ignition on. ABS light should come on, then go out after 3 seconds. If warning light does not come on, check fuse, bulb, and wiring harness.

2) With ignition on, remove short pin from Data Link Connector (DLC). See Fig. 4. Connect jumper wire between DLC terminals Tc and E1. See Fig. 4. If a malfunction is detected, 4 seconds will elapse, then ABS light will begin to flash a 2-digit code. First series of flashes indicates first digit of code. After a 1.5-second pause, second series of flashes indicates second digit of code.

3) If 2 or more codes are stored, there will be a 2.5-second pause between each code. After all codes are displayed, a 4-second pause will occur, then all codes will repeat. If ABS system is functioning properly, ABS light will flash 2 times every second. For code interpretation, see DIAGNOSTIC CODES.

4) After replacing or repairing malfunctioning components, clear diagnostic codes. If a battery cable was disconnected during repairs, all codes will be erased. If battery cable was not disconnected during repairs, see CLEARING CODES.

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Fig. 4: Identifying Data Link Connector (DLC) Terminals (Courtesy of Toyota Motor Sales, U.S.A., Inc. )

DIAGNOSTIC CODES

Check suspect components in order given. Checks consist mainly of a visual inspection and continuity tests.

Code 11

Open in solenoid relay circuit.

Check actuator wiring harness, solenoid relay, solenoid relay wiring harness and solenoid relay connector. See SOLENOID RELAY under COMPONENT TESTING.

Code 12

Short in solenoid relay circuit.

Check actuator wiring harness, solenoid relay, solenoid relay wiring harness and solenoid relay connector. See SOLENOID RELAY under COMPONENT TESTING.

Code 13

Open in pump motor relay circuit.

Check actuator wiring harness, pump motor relay, pump motor relay wiring harness and pump motor relay connector. See MOTOR RELAY under COMPONENT TESTING.

Code 14 Short in pump motor relay circuit.

Check actuator wiring harness, pump motor relay, pump motor relay wiring harness and pump motor relay connector. See MOTOR RELAY under COMPONENT TESTING.

Code 21

Open or short circuit in solenoid for right front wheel.

Check actuator solenoid, wiring harness and connector. See ACTUATOR CHECK under DIAGNOSIS & TESTING. See ABS ACTUATOR under COMPONENT TESTING.

Code 22

Open or short circuit in solenoid for left front wheel.

Check actuator solenoid, wiring harness and connector. See ACTUATOR CHECK under DIAGNOSIS & TESTING. See ABS ACTUATOR under COMPONENT TESTING.

Incomplete WORK IN PROGRESS ***