ANTI-LOCK BRAKE SYSTEM - REAR WHEEL

Size: px

Start display at page:

Download "ANTI-LOCK BRAKE SYSTEM - REAR WHEEL"

Hilary Hawkins
6 years ago
Views:

ANTI-LOCK BRAKE SYSTEM - REAR WHEEL 1994 Nissan Pickup 1994 BRAKES Nissan - Rear Anti-Lock Pathfinder, Pickup DESCRIPTION In 2WD mode, Rear Anti-Lock Brake System (RABS) helps the driver to maintain

1 ANTI-LOCK BRAKE SYSTEM - REAR WHEEL 1994 Nissan Pickup 1994 BRAKES Nissan - Rear Anti-Lock Pathfinder, Pickup DESCRIPTION In 2WD mode, Rear Anti-Lock Brake System (RABS) helps the driver to maintain steering control during heavy braking by fluctuating rear brakeline pressure. This prevents rear wheel lock-up and skidding in the event of front wheel lock-up. In 4WD mode, RABS will not prevent rear wheel lock-up if front wheels lock. System consists of an Electronic Control Unit (ECU) with an LED that displays self-diagnostic codes, a rear wheel speed sensor, actuator (electro-hydraulic unit) and an ANTI-LOCK warning light located on instrument cluster. See Fig. 1. See RABS ELECTRICAL COMPONENT LOCATIONS table. ANTI-LOCK warning light warns driver of problem in ABS. If test terminal of check connector is grounded when warning light is on, LED on ECU will flash to indicate trouble codes. See Fig. 4. RABS ELECTRICAL COMPONENT LOCATIONS TABLE Component Location ECU... Behind Center Of Instrument Panel Ignition Relay No Below Passenger Compartment Fuse Block Rear Wheel Speed Sensor... On Differential Companion Flange NOTE: For more brake system information, see BRAKE SYSTEM article in the BRAKES section. BRAKE SYSTEM - Pathfinder BRAKE SYSTEM - Pickup Fig. 1: Locating Rear Anti-Lock Brake System Components

2 OPERATION NOTE: In 4WD mode, rear wheels will lock if front wheels lock. If this occurs, ANTI-LOCK warning light will come on. This is not a malfunction. Warning light will reset if engine is turned off and then started again. When vehicle is moving, rear wheel speed sensor sends an AC signal to the ECU. When brake pedal is applied, ECU receives signal through brakelight switch. When this occurs, ECU will monitor deceleration rate of rear wheels through rear wheel speed sensor. Sensor is located on front of rear differential. See Figs. 1 and 8. If rear wheel deceleration rate reaches a preprogrammed rate (with vehicle in 2WD mode), the ECU activates the solenoid valves inside the actuator (electro-hydraulic unit). Solenoid valves are cycled to apply, release or maintain hydraulic pressure to each rear wheel brake caliper/wheel cylinder depending upon signals from ECU. Regulating hydraulic pressure to each caliper/wheel cylinder prevents rear wheel lock-up. When brake pedal is released, ECU deactivates solenoid valves, and system returns to conventional brake system operation until ABS is needed. CAUTION: See ANTI-LOCK BRAKE SAFETY PRECAUTIONS article in the GENERAL INFORMATION section. BLEEDING BRAKE SYSTEM Turn ignition off. Disconnect actuator connectors. Bleed brake system in a conventional manner using the following sequence: * Left rear caliper or wheel cylinder. * Right rear caliper or wheel cylinder. * Left front caliper. * Right front caliper and bleeder on RABS actuator. ADJUSTMENTS BRAKE PEDAL HEIGHT & FREE PLAY 1) Lift up carpet and insulator. Measure pedal height from pressure face of pedal pad to floor pan. If pedal height is not as specified, loosen brake booster input rod lock nut. See BRAKE PEDAL HEIGHT SPECIFICATIONS table. 2) Rotate input rod to obtain proper pedal height. Tighten lock nut. Adjust brakelight switch. See BRAKELIGHT & CRUISE CONTROL SWITCHES under ADJUSTMENTS. Ensure pedal free play is " ( mm). BRAKE PEDAL HEIGHT SPECIFICATIONS TABLE Application In. (mm) Automatic Transmission ( ) Manual Transmission ( ) LOAD-SENSING PROPORTIONING VALVE NOTE: If pressure cannot be adjusted to specification, replace

3 entire valve assembly. Pressure Adjustment 1) Ensure vehicle is in unladen condition. Have one person sit in driver s seat. To stabilize suspension deflection, have one person sit on rear of vehicle and then get off vehicle slowly. 2) Attach a lever to Load-Sensing Proportioning Valve (LSPV) stopper bolt. See Fig. 2. Adjust spring length to about 7.44" (189 mm). Install 2 Pressure Gauges (KV991V0010), one to front brake bleeder and one to rear brake bleeder. Fig. 2: Adjusting Load-Sensing Proportioning Valve (LSPV) 3) Bleed air from front and rear bleeders. Depress brake pedal until front brake pressure reading is 1422 psi (100 kg/cm ). Check rear brake pressure. Ensure rear brake pressure is within specification. See LSPV PRESSURE SPECIFICATIONS table. 4) Slowly set a 221 lbs. (100 kg) weight on rear of vehicle, near axle center. Depress brake pedal until front brake pressure reading is 1422 psi (100 kg/cm ). Rear brake pressure reading should be as specified. See LSPV PRESSURE SPECIFICATIONS table. If pressure readings are not correct, adjust spring bracket using adjusting bolts. See Fig. 2. Repeat test. LSPV PRESSURE SPECIFICATIONS TABLE Application Front Brake Rear Brake Pressure Pressure psi (kg/cm ) psi (kg/cm ) 2.4L

4 With Weight (1) (100)... (2) (36-49) Without Weight (100) (30-38) 3.0L Except Heavy Duty With Weight (1) (100) (42-56) Without Weight (100) (31-39) Heavy Duty With Weight (1) (100) (40-54) Without Weight (100) (31-39) (1) - Weight is 221 lbs. (100 kg) above rear axle center. (2) psi (34-48 kg/cm ) for Canadian vehicles. PARKING BRAKE Adjustment (Rear Disc Brake) 1) Release parking brake lever. Using a screwdriver, rotate parking brake shoe adjuster wheel until parking brake shoes contact drum. Back off adjuster wheel 7-8 notches. Ensure shoes do not drag on drum. 2) Raise and support rear of vehicle. Cable adjuster is under vehicle. Turn cable adjuster until parking brake lever can be pulled up the appropriate number of strokes (notches) with 44 lbs. (20 kg) of force applied to lever. See PARKING BRAKE LEVER STROKE SPECIFICATIONS table. After releasing lever, ensure rear wheels rotate freely. PARKING BRAKE LEVER STROKE SPECIFICATIONS TABLE Application Notches Pathfinder Pickup Center Lever Type Stick Lever Type 2WD WD Adjustment (Rear Drum Brake) Raise and support rear of vehicle. Adjust brake shoe-to-drum clearance. Cable adjuster is under vehicle. Turn cable adjuster until parking brake lever can be pulled up appropriate number of strokes (notches) with 44 lbs. (20 kg) of force applied to lever. See PARKING BRAKE LEVER STROKE SPECIFICATIONS table. After releasing lever, ensure rear wheels rotate freely. POWER BRAKE UNIT OUTPUT ROD Apply 20 in. Hg vacuum to power brake unit with hand-held vacuum pump. See Fig. 3. Measure length of output rod extending from power brake unit housing. Adjust output rod if length is not " ( mm). If length cannot be adjusted, replace power brake unit.

5 Fig. 3: Measuring Output Rod Length BRAKELIGHT & CRUISE CONTROL SWITCHES Switches are on brake pedal bracket. Adjust brake pedal height. See BRAKE PEDAL HEIGHT & FREE PLAY under ADJUSTMENTS. If clearance between brake pedal stopper and switch is not " ( mm), loosen lock nut. Turn switch body until clearance is as specified. Tighten lock nut. TROUBLE SHOOTING ANTI-LOCK WARNING LIGHT System Operational Check 1) Turn ignition on. ANTI-LOCK warning light on instrument cluster should come on. If light does not come on, check bulb and circuit. If light comes on, start engine. Warning light should go out. 2) If warning light stays on after starting engine, go to RETRIEVING CODES under DIAGNOSIS & TESTING. If warning light goes off after engine is started, drive vehicle at 25 MPH or faster for at least one minute. If warning light stays off, no faults have been detected by ECU. 3) If warning light comes on during road test, go to RETRIEVING CODES under DIAGNOSIS & TESTING. If warning light does not come on after engine is started and a problem exists, diagnose by symptom. Go to SYMPTOM DIAGNOSTICS under TROUBLE SHOOTING. SYMPTOM DIAGNOSTICS Pedal Vibration & Noise

6 1) If symptom appears only under sudden brake application, press pedal normally. If symptom is gone, RABS is okay. If symptom appears when brake is applied normally, go to next step. 2) If noise appears and warning light activates and deactivates only when ignition is turned on, RABS is functioning correctly. If noise appears with ignition off, check brake pedal and hydraulic system. Long Stopping Distance 1) Check road condition. If road condition is slippery or gravelly, stopping distance will be longer than normal. If road condition is not slippery or gravelly, disconnect actuator connector. Recheck stopping distance. 2) If stopping distance is still too long, inspect brake system and bleed hydraulic system. See BLEEDING BRAKE SYSTEM. If stopping distance is now normal, reconnect actuator connector. Go to PRELIMINARY INSPECTION under DIAGNOSIS & TESTING, and perform selfdiagnostics. Pedal Stroke Too Long Check frequency of symptom. If symptom appears occasionally, this may not be a malfunction indication (length of brake pedal stroke tends to increase during RABS operation). If symptom appears regularly, bleed hydraulic system. See BLEEDING BRAKE SYSTEM. Inspect condition of brake mechanical components. ABS Does Not Work 1) If ANTI-LOCK warning light comes on, go to PRELIMINARY INSPECTION under DIAGNOSIS & TESTING, and perform self-diagnostics. If ANTI-LOCK warning light does not come on, go to next step. 2) Ensure vehicle is not in 4WD mode, and vehicle speed is greater than 6 MPH. RABS does not work in 4WD mode or at speeds less than 6 MPH. 3) Check parking brake switch and brakelight switch operation and adjustment. Replace or adjust switches as necessary. If parking brake switch and brakelight switch are okay and RABS still does not work, go to next step. 4) Check actuator and rear wheel speed sensor. See ACTUATOR and REAR WHEEL SPEED SENSOR under DIAGNOSIS & TESTING. Repair or replace components as necessary. If actuator and speed sensor are okay, check ECU power and ground circuits. See ECU POWER & GROUND CIRCUITS under DIAGNOSIS & TESTING. Repair as necessary. If ECU power and ground circuits are okay, replace ECU. ABS Works Frequently 1) Check brake fluid pressure differential. See PROPORTIONING VALVE under DIAGNOSIS & TESTING. If pressure differential is okay, go to next step. If pressure differential is not to specification, replace master cylinder. 2) Check brake system thoroughly. Repair or replace components as necessary. If brake system is okay, RABS should be operating correctly. NOTE: Frequent RABS operation is normal under severe braking conditions where wheel lock-up would occur. DIAGNOSIS & TESTING NOTE: To prevent terminal damage, backprobe terminals when connecting test meter leads to ECU connector. PRELIMINARY INSPECTION

7 Preliminary Check No. 1 1) Turn ignition on. If ANTI-LOCK warning light comes on, go to next step. If warning light does not come on, check ECU power and ground circuits. See ECU POWER & GROUND CIRCUITS under DIAGNOSIS & TESTING. If power and ground circuits are okay, replace ECU. 2) Wait a few seconds. If warning light goes out after a few seconds and remains out, go to next step. If warning light remains on, or goes out and then comes on again, go to PRELIMINARY CHECK NO. 2. 3) Drive vehicle in 2WD mode at speeds greater than 25 MPH for at least one minute. If warning light comes on during road test, go to PRELIMINARY CHECK NO. 2. If warning light does not come on during road test, stop engine. 4) Turn ignition on and listen for actuator clicking when warning light goes out. If actuator clicks when warning light goes out, RABS is okay. If actuator does not click when warning light goes out, check actuator. See ACTUATOR under DIAGNOSIS & TESTING. Preliminary Check No. 2 1) Leave engine running if it was started. Ground test terminal No. 3 (Red/Green wire) of check connector. See Fig. 4. Observe LED on ECU. If LED begins flashing, go to RETRIEVING CODES under DIAGNOSIS & TESTING. If LED does not start flashing, go to next step. 2) Check brake fluid level. Add fluid as necessary. If fluid level is okay, check ECU power and ground circuits. See ECU POWER & GROUND CIRCUITS under DIAGNOSIS & TESTING. If ECU power and ground circuits are okay, replace ECU. Fig. 4: Grounding Check Connector Test Terminal RETRIEVING CODES NOTE: Before retrieving codes, perform PRELIMINARY CHECK NO. 1. See PRELIMINARY INSPECTION under DIAGNOSIS & TESTING. Drive vehicle in 2WD mode at speeds greater than 25 MPH for at least one minute. Ground check connector test terminal No. 3 (Red/Green wire). See Fig. 4. Observe LED on ECU. See Fig. 1. Count the number of flashes to identify code. LED pauses for 5-10 seconds before repeating code. See ABS WARNING CODE DIRECTORY table. LED will only indicate ONE code at a time. After problem circuit has been repaired, check for remaining codes. ABS WARNING CODE DIRECTORY TABLE Code Problem Detected Figure 2 ISO Solenoid Open Circuit See Fig. 9

8 3 DUMP Solenoid Open Circuit See Fig ISO Solenoid Blocked See Fig Brake Mechanical (1) 6 Speed Sensor Signal Erratic See Fig ISO Solenoid Short Circuit See Fig. 9 8 DUMP Solenoid Short Circuit See Fig Speed Sensor Open Circuit See Fig Speed Sensor Short Circuit See Fig , 14 & 15 ECU (2) (1) - Overhaul rear brake assemblies. Perform PRELIMINARY CHECK NO. 2. See PRELIMINARY INSPECTION under DIAGNOSIS & TESTING. If Code 5 is still present, replace actuator. (2) - Replace ECU. ACTUATOR Operational Test 1) Perform PRELIMINARY CHECK NO. 2. See PRELIMINARY INSPECTION under DIAGNOSIS & TESTING. If actuator clicks when warning light goes out, go to step 5). If actuator does not click when warning light goes out, go to next step. 2) Using a voltmeter, measure voltage between ECU connector terminals No. 1 (positive) and No. 11 (negative). See Fig. 5. Turn ignition on. When ANTI-LOCK warning light goes out, voltage should pulse from.3 volt to 3.5 volts for about 13 milliseconds. 3) Repeat voltage pulse test between ECU connector terminals No. 17 (positive) and No. 11 (negative). Voltage should pulse from.3 volt to 3.5 volts for about 13 milliseconds. 4) If voltage pulses as specified, replace actuator. If voltage does not pulse as specified in either test, replace ECU. 5) Drive vehicle at 25 MPH or faster for at least one minute in 2WD mode. If ANTI-LOCK warning light comes on during road test, go to RETRIEVING CODES under DIAGNOSIS & TESTING. If warning light does not come on during road test, go to next step. 6) Check ordinary braking. Apply brakes sufficiently to lock front wheels. If rear wheels also lock, replace actuator. If rear wheels do not lock when front wheels lock, RABS is functioning correctly.

9 Fig. 5: Checking For Pulsing Voltage From ECU ECU POWER & GROUND CIRCUITS CAUTION: Before servicing ECU, ground yourself and work area to discharge stored electricity. As little as a 30-volt charge created by static electricity can cause a total or degrading failure in ECU or other electronic components containing integrated circuits. 1) Disconnect ECU connector. Turn ignition on. Check for battery voltage between ECU connector terminals No. 2 and 11. See Fig. 5. If battery voltage is present, go to step 3). If battery voltage is not present, check continuity between ECU connector terminal No.11 and ground. 2) If there is no continuity, repair circuit. If there is continuity, check for blown fuse, burned out ANTI-LOCK warning light bulb, defective relay or faulty wiring. See RELAYS under DIAGNOSIS & TESTING. 3) Turn ignition off. Reconnect ECU connector. Turn ignition

10 on. Measure voltage between ECU connector terminals No. 11 and 12. If battery voltage is not present, check fuse, relay and wiring harness. See RELAYS under DIAGNOSIS & TESTING. 4) If battery voltage is present, measure voltage between ECU connector terminals No. 8 and 11. Battery voltage should be present with brake pedal pressed. Battery voltage should not be present with brake pedal released. 5) If voltage is as specified, go to next step. If voltage is not as specified, adjust brakelight switch. See BRAKELIGHT & CRUISE CONTROL SWITCHES under ADJUSTMENTS. If adjustment is correct, replace switch or repair harness. 6) Ensure brake fluid level is correct. Release parking brake. Check for battery voltage between ECU connector terminals No. 5 and 11. If battery voltage is present, go to next step. If battery voltage is not present, adjust parking brake switch. If switch adjustment is correct, replace switch or repair harness and/or connectors. 7) Set parking brake. Voltage should drop to about zero volts. If voltage drops as specified, ECU power and ground circuits are okay. If voltage does not drop, check parking brake switch, harness and/or connectors. PROPORTIONING VALVE Pressure Testing Connect pressure gauges to front and rear brake bleeders. Bleed air from hydraulic system. Press brake pedal until front pressure is as specified. See PROPORTIONING VALVE PRESSURE SPECIFICATIONS table. Check rear pressure. If rear pressure is within specification, proportioning valve is okay. If rear pressure is not within specification, replace master cylinder. PROPORTIONING VALVE PRESSURE SPECIFICATIONS TABLE Application Front Brake Rear Brake Pressure Pressure psi (kg/cm ) psi (kg/cm ) Pathfinder Rear Disc Brake (69) (49-57) Rear Drum Brake (69) (40-48) Pickup (69) (23-30) RELAYS Ignition Relay No. 2 (With Power Windows And/Or Adjustable Shock Absorbers) Remove relay. Check continuity between relay terminals No. 3 and 5, and between terminals No. 6 and 7. See Fig. 6. Continuity should not be present. Apply battery voltage between terminals No. 1 and 2. Continuity should be present between terminals No. 3 and 5, and between terminals No. 6 and 7. Replace relay if continuity is not as specified.

11 Fig. 6: Ignition Relay No. 2 Terminals (With Power Windows Or Adjustable Shock Absorbers) Ignition Relay No. 2 (Without Power Windows Or Adjustable Shock Absorbers) Remove relay. Check continuity between relay terminals No. 3 and 5. See Fig. 7. Continuity should not be present. Apply battery voltage between terminals No. 1 and 2. Continuity should be present between relay terminals No. 3 and 5. Replace relay if continuity is not as specified. Fig. 7: Ignition Relay No. 2 Terminals (Without Power Windows Or Adjustable Shock Absorbers) REAR WHEEL SPEED SENSOR

12 Signal Voltage Test 1) Raise and support rear of vehicle with wheels off ground. Start engine. Shift transmission into Drive (A/T) or 1st gear (M/T). Allow rear wheels to rotate with engine idling at about 830 RPM (A/T) or 620 RPM (M/T). 2) Check AC voltage between ECU connector terminals No. 9 and 10. See Fig. 5. If AC voltage is.4 volt or greater, signal voltage is okay. If AC voltage is less than.4 volt, turn engine off. 3) Inspect condition of sensor rotor teeth. Check sensor rotor installation on companion flange. Check rotor for deformation, wear and looseness. If rotor is okay, replace sensor unit. If rotor is damaged, replace rotor and companion flange as a set. See WHEEL SPEED SENSOR under REMOVAL & INSTALLATION. REMOVAL & INSTALLATION ACTUATOR Removal & Installation Disconnect negative battery cable. Drain brake fluid. Disconnect electrical connectors and brakelines from actuator. Remove actuator mounting nuts. Remove actuator. To install, reverse removal procedure. Bleed brake system. See BLEEDING BRAKE SYSTEM. ELECTRONIC CONTROL UNIT (ECU) CAUTION: Before servicing ECU, ground yourself and ground the work area to discharge stored electricity. As little as a 30-volt charge created by static electricity can cause a total or degrading failure in ECU or other electronic components containing integrated circuits. Removal Disconnect negative battery cable. Remove lower center trim from instrument panel. Disconnect ECU connector. Remove bolts and ECU. Installation To install, reverse removal procedure. WHEEL SPEED SENSOR Removal & Installation 1) Disconnect negative battery cable. Raise and support rear of vehicle. Disconnect drive shaft from rear differential companion flange. See Fig. 8. 2) Remove companion flange nut and companion flange. DO NOT damage sensor rotor mounted on companion flange. If rotor is damaged, replace companion flange and rotor as a set. Remove bolts and sensor unit. To install components, reverse removal procedure.

13 Fig. 8: Exploded View Of Rear Wheel Speed Sensor Unit TORQUE SPECIFICATIONS TORQUE SPECIFICATIONS TABLE Application Ft. Lbs. (N.m) Actuator Mounting Nuts (37-50) Companion Flange Nut ( ) Drive Shaft-To-Companion Flange Nuts (79-88) Hydraulic Brake Lines At Actuator (15-18) Wheel Lug Nuts ( ) INCH Lbs. (N.m) Wheel Speed Sensor Unit Mounting Bolt (8-11) SELF-DIAGNOSTIC CHARTS

14 Fig. 9: Codes No. 2 & 7

15 Fig. 10: Codes No. 3 & 8

16 Fig. 11: Code No. 4 Fig. 12: Code No. 6

17 Fig. 13: Codes No. 9 & 10 WIRING DIAGRAM

18 Fig. 14: Rear Anti-Lock Brake System (RABS) Wiring Diagram

1994 Mazda MX-5 Miata. ANTI-LOCK BRAKE SYSTEM 1994 BRAKES Mazda - Anti-Lock

1994 Mazda MX-5 Miata. ANTI-LOCK BRAKE SYSTEM 1994 BRAKES Mazda - Anti-Lock ANTI-LOCK BRAKE SYSTEM 1994 BRAKES Mazda - Anti-Lock DESCRIPTION The Anti-Lock Brake System (ABS) control unit senses reductions in front and rear wheel speed and modulates hydraulic pressure to the brakes