Halderman ch107 lecture

© 2011 Pearson Education, Inc.All Rights Reserved

Automotive Technology, Fourth EditionJames Halderman

ABS DIAGNOSIS AND REPAIR

107

107 ABS DIAGNOSIS AND SERVICE



ObjectivesObjectives

• The student should be able to:– Prepare for Brakes (A5) ASE certification

test content area “F” (Antilock Brake System Diagnosis and Repair).

– Explain the purpose and function of the red brake warning lamp.

– Describe normal ABS dash lamp operation. – Discuss visual inspection of the various

types and brands of ABS.




ObjectivesObjectives

• The student should be able to:– Explain how to retrieve trouble codes.– List the methods used to clear trouble

codes. – Explain the various methods for bleeding

ABS systems. – Discuss methods and tools needed to

diagnose and service an ABS-equipped vehicle.




ABS DIAGNOSTIC ABS DIAGNOSTIC PROCEDUREPROCEDURE




ABS Diagnostic ProcedureABS Diagnostic Procedure

• To diagnose an ABS problem use the following steps:– STEP 1: Verify the customer concern.– STEP 2: Perform a visual inspection

including leaks or faults in the following:• Master cylinder• Electrohydraulic control unit





• To diagnose an ABS problem use the following steps:– STEP 2: Perform a visual inspection

including leaks or faults in the following:• Flexible brake hoses






including leaks or faults in the following:• Brake lines and fittings






including leaks or faults in the following:• Calipers and/or wheel cylinders





• To diagnose an ABS problem use the following steps:– STEP 3: Check for stored diagnostic trouble

codes.– STEP 4: Complete the repair.– STEP 5: Verify the repair.




BRAKE WARNINGBRAKE WARNINGLAMP OPERATIONLAMP OPERATION




Brake Warning Lamp OperationBrake Warning Lamp Operation

• When visually diagnosing an antilock braking system problem first check the status of the brake warning lamps





• Red Brake Warning Lamp– A red brake warning lamp (RBWL) warns of

a possible dangerous failure in the base brakes





• Red Brake Warning Lamp– This lamp will also light if the parking brake

is applied and may light due to an ABS failure





• Amber ABS Warning Lamp– The amber ABS warning lamp usually

comes on after an engine start during the initialization or start-up self-test sequence

– The amount of time the lamp remains on after the ignition is turned on varies with design




Figure 107-1 On most vehicles equipped with ABS, the amber ABS and red BRAKE warning lamp should come on as a bulb check when the ignition is first switched on.




THOROUGH VISUALTHOROUGH VISUALINSPECTIONINSPECTION




Thorough Visual InspectionThorough Visual Inspection

• A thorough visual inspection should include the following items:– Brake fluid level: check condition and level– Brake fluid leaks: check for cracks or other

damage in flexible lines damage and check for wetness at any fitting or steel brake line





• A thorough visual inspection should include the following items:– Fuses and fusible links: check all ABS-

related fuses– Wiring and connections: check all wiring,

especially wheel speed sensor leads





• A thorough visual inspection should include the following items:– Wheel speed sensors: check that the

sensor ring teeth are not damaged and clean debris from the sensor if possible





• NOTE: Most wheel speed sensors are magnetic and therefore can attract and hold metallic particles. Be sure to remove any metallic debris from around the magnetic wheel speed sensor.





• A thorough visual inspection should include the following items:– Base brake components: check that all

base brake components, including disc brake calipers, drum brake wheel cylinders, and related components are in good working condition





• A thorough visual inspection should include the following items:– Parking brake: check that the brake is

correctly adjusted and fully released





• A thorough visual inspection should include the following items:– Wheel bearings: check that all wheel

bearings are free of defects and adjusted properly





• A thorough visual inspection should include the following items:– Wheels and tires: check for correct size,

proper inflation, and legal tread depth

?




Figure 107-2 A thorough visual inspection should include carefully inspecting around the electrohydraulic unit for signs of obvious problems or the installation of aftermarket devices such as alarm systems.




TEST DRIVE TEST DRIVE AND VERIFYAND VERIFYTHE FAULTTHE FAULT




Test Drive and Verify the FaultTest Drive and Verify the Fault

• Many ABS systems and diagnostic trouble codes (DTCs) will not set unless the vehicle is moving

• Start the engine and observe the red and amber brake warning lamps

• If the red brake warning lamp is on, the base brakes may not be functioning correctly





• NOTE: Some ABS units, such as the Delphi VI, will cause the brake pedal to move up and down slightly during cycling of the valves during the self-test. Each system has unique features. The service technician will have to learn to avoid attempting to repair a problem that is not a fault of the system.





• NOTE: Some systems are diagnosed by “antilock” and “brake” warning lamps, vehicle symptoms, and the use of a breakout box.




RETRIEVING RETRIEVING DIAGNOSTICDIAGNOSTIC

TROUBLE CODESTROUBLE CODES




Retrieving Diagnostic Trouble CodesRetrieving Diagnostic Trouble Codes

• The exact procedure depends on the type of ABS and vehicle

• Always consult factory service information for the vehicle being diagnosed





• Some systems can only display flash codes (flashing ABS or brake lamp in sequence)

• Some systems can perform self-diagnosis and display all information on a scan tool





• NOTE: With some early antilock braking systems, the diagnostic trouble code is lost if the ignition is turned “off” before grounding the diagnostic connector.




KELSEY-HAYES KELSEY-HAYES ANTILOCKANTILOCK

(NONINTEGRAL)(NONINTEGRAL)




Kelsey-Hayes Antilock (Nonintegral)Kelsey-Hayes Antilock (Nonintegral)

• The Kelsey-Hayes rear-wheel antilock uses two solenoids and valves to control the rear-wheel brakes

• Kelsey-Hayes four-wheel antilock uses the computer to pulse the valves

• This pumping is called pulse-width modulated (PWM) and the valve is called a PWM valve





• GM trucks’ (RWAL) DTCs are retrieved by flash codes or scan data through the use of a scan tool or connect H to A at the data link connector (DLC)

• Ford RABS DTCs are retrieved by jumper lead flash codes only

• Dodge light truck DTCs are retrieved by ground diagnostic connections





• NOTE: Be sure that the brake warning lamp is on before trying to retrieve DTCs. If the lamp is not on, a false code 9 could be set.





• NOTE: If the ignition is turned off, the failure code will be lost unless it is a hard code that will be present when the ignition is turned back on.





• NOTE: A scan tool may or may not be able to retrieve or display diagnostic trouble codes. Check with the technical literature for the specific vehicle being scanned.




Figure 107-3 General Motors diagnostic connector on a pre- 1996 vehicle. Flash codes are available by using a jumper wire to ground (terminal A) to terminal H.




Figure 107-4 Connecting a jumper wire from the diagnostic connector to ground. The exact location of this diagnostic connector varies with the exact vehicle model and year.




Figure 107-5 Chrysler diagnostic connector location varies with the model and year.




BOSCH 2 ABSBOSCH 2 ABS(NONINTEGRAL)(NONINTEGRAL)




Bosch 2 ABS (Nonintegral)Bosch 2 ABS (Nonintegral)

• Retrieving Diagnostic Trouble Codes– On General Motors vehicles connect A to H

at the data link connector (DLC)– For most systems, a scan tool should be

used, if available




TEVES MARK IVTEVES MARK IV




Teves Mark IVTeves Mark IV

• The Teves Mark IV is a nonintegral (remote) ABS system– Retrieving diagnostic trouble codes

• Only a bidirectional scan tool connected to the data link connector (DLC) can be used




Figure 107-6 A scan tool is the recommended method to use to access General Motors Teves Mark IV systems.





• The Teves Mark IV is a nonintegral (remote) ABS system– Clearing diagnostic trouble codes

• On some vehicles, a scan tool is required






• Driving over 20 mph (32km/h) will clear codes on some vehicles






• Disconnecting the battery will clear the codes, but will cause loss of other "keep alive" functions




DELPHI (DELCO) DELPHI (DELCO) ABS-VIABS-VI

(NONINTEGRAL)(NONINTEGRAL)




Delphi (Delco) ABS-VI (Nonintegral)Delphi (Delco) ABS-VI (Nonintegral)

• The Delphi (Delco) ABS-VI is unique from all other ABS systems because it uses a motor-driven ball screws and pistons for brake pressure to reduce, hold, and apply




Delphi (Delco) ABS-VI (Nonintegral)Delphi (Delco) ABS-VI (Nonintegral)

• Retrieving Diagnostic Codes– This system has extensive self-diagnostic

capability– A scan tool designed to work with the

Delphi VI system is required to access this information




Figure 107-7 The Delphi (Delco) VI attaches to the side of the master cylinder and connects hydraulically through transfer tube assemblies.




WHEEL SPEEDWHEEL SPEEDSENSOR DIAGNOSISSENSOR DIAGNOSIS




Wheel Speed Sensor DiagnosisWheel Speed Sensor Diagnosis

• Wheel speed sensor (WSS) circuits are often the cause of many ABS problems

• These components may suffer from physical damage, buildup of metallic debris on the sensor tip, corrosion, poor electrical connections, and damaged wiring





• Test a WSS by measuring its output voltage and circuit continuity

• A breakout box (BOB) cable connects to the ABS harness near the ABS module

• All WSS resistance checks, including the wiring to the sensors, can be measured at one location




Figure 107-8 A breakout box is being used to diagnose an ABS problem. The controller (computer) is located in the trunk of this vehicle, and a digital multimeter is being used to measure resistance and voltage at various points in the system, following the service manual procedure.




Figure 107-9 Typical wheel speed sensor. When a tooth on the sensor ring is close to the sensor, the strength of the magnetic field is stronger because the metal of the tooth conducts magnetic lines of force better than air. When the tooth moves away, the magnetic field strength is reduced. It is this changing magnetic field strength that produces the changing voltage. Frequency of the signal is determined by the speed of the rotating sensor.





• Resistance Measurement– The resistors of most WSS range from 800

Ω to 1,400 Ω– A reading of about 1,000 ohms or 1 KΩ

indicates proper sensor coil resistance




Figure 107-10 Measuring the resistance of a wheel speed sensor.





• Checking For Short-To-Ground– Connect either lead of an ohmmeter to one

of the WSS wires and the other to a good, clean chassis ground





• Checking For Short-To-Ground– The resistance should be infinity (OL)– If resistance reading is low the sensor or

sensor wiring must be replaced





• AC Voltage Check– Connect a digital meter to the WSS

terminals or input to the controller in the breakout box and set the meter to read AC volts

– Rotate the wheel by hand at a rate of one revolution per second





• AC Voltage Check– A good WSS should produce voltage of at

least 0.1 volt (100 mV)– A sensor voltage of lower than 0.1 volt (100

mV) may be caused by three things:1. Excessive clearance between the sensor

and tone ring.





• AC Voltage Check– A sensor voltage of lower than 0.1 volt (100

mV) may be caused by three things:2. Buildup of debris on the end of the sensor.





• AC Voltage Check– A sensor voltage of lower than 0.1 volt (100

mV) may be caused by three things:3. Excessive resistance in the sensor or

sensor wiring.





• DC Bias Voltage– Some ABS systems apply a 2.5 volt DC

voltage to the wheel speed sensors, called a bias voltage





• DC Bias Voltage– Bias voltage is used by the ABS controller

to detect fault in the sensor or sensor wiring such as an open circuit or a short to ground





• Scope Testing– Attach the scope leads to the sensor

terminals or to the input connector on the breakout box

– Rotate the wheel by hand or by using engine power with all four wheels off the ground





• Scope Testing– A good WSS should produce an alternating

current (AC) sine wave signal that increases in frequency and amplitude with increasing wheel speed

– Damaged or missing teeth on the tone ring will cause flat spots or gaps in the sine wave pattern





• Scope Testing– A bent axle or hub will produce a wavelike

pattern that fluctuates as the strength of the sensor signal changes with each revolution




Figure 107-11 A scope can be used to check for proper operation of a wheel speed sensor.




Figure 107-12 A broken tooth on a wheel speed sensor tone ring shows on the scope trace as a missing wave.





• Scan Tool Testing– As an assistant drives the vehicle, connect

the scan tool and monitor the speed of all of the sensors





• Scan Tool Testing– All sensors should indicate the same speed– If all sensors do not show the same speed,

carefully check the tone ring for damage




WHEEL SPEED SENSORWHEEL SPEED SENSORADJUSTMENTADJUSTMENT




Wheel Speed Sensor AdjustmentWheel Speed Sensor Adjustment

• Most sensors adjust by loosening a set screw and inserting a nonmagnetic brass or plastic feeler gauge between the tip of the sensor and a high point on the tone ring





• Adjust the position of the sensor so there is a slight drag on the feeler gauge, and then tighten the setscrew to lock the sensor in place





• New sensors have a piece of paper or plastic on the tip end of the unit, which must be left in place during installation to guarantee a correct air gap between the tip of the sensor and the tone ring





• Adjust the sensor so the tip just touches the tone ring and you can slip the paper or plastic out without ripping it

• Tighten the setscrew and the air gap is properly set




Figure 107-13 Use a nonmagnetic brass or plastic feeler gauge to check wheel speed sensor gap. A steel gauge would be attracted by the magnet in the sensor and would produce a drag on the gauge as it is moved between the sensor and the tone ring. This drag could be interpreted as a correct clearance reading.




Figure 107-14 (a) Always use a nonferrous (brass or plastic) feeler (thickness) gauge when measuring the gap between the toothed ring and the wheel speed sensor.




Figure 107-14 (b) Sometimes a sensor is equipped with a paper spacer that is the exact thickness of the spacing required between the toothed ring and the sensor. If equipped, the sensor is simply installed with the paper touching the toothed wheel. A typical gap ranges from 0.020 to 0.050 in. (0.5 to 1.3 mm).





• Digital Wheel Speed Sensor Diagnosis– Check that battery voltage is available at

the sensor with the key on, engine off





• Digital Wheel Speed Sensor Diagnosis– If the sensor does not have 12 volts, then

the problem is most likely in the ABS controller or the wiring between the controller and the sensor





• Digital Wheel Speed Sensor Diagnosis– If there are 12 volts at the sensor, measure

the signal voltage– The voltage should switch from about 0.8V

to about 1.9V as the wheel is rotated by hand




OBD-II ABS DIAGNOSIS OBD-II ABS DIAGNOSIS




OBD-II ABS DiagnosisOBD-II ABS Diagnosis

• Vehicles 1996 and Newer– The OBD-II diagnostic connector is used to

transmit ABS diagnostic trouble code information to a scan tool





• Vehicles 1996 and Newer– A factory scan tool or an enhanced factory

level scan tool will be needed to retrieve ABS diagnostic trouble codes (DTCs) and scan tool data





• Scan Tools Needed For ABS Diagnosis– Scan tools can be divided into two basic

groups:1. Factory scan tools are required by all

dealers that sell and service the brand of vehicle. Examples include the following:– General Motors —Tech 2







dealers that sell and service the brand of vehicle. Examples include the following:– Ford —New Generation Star (NGS) and IDS

(Integrated Diagnostic Software)







dealers that sell and service the brand of vehicle. Examples include the following:– Chrysler —DRB III, Star Scan or wiTECH for

CAN-equipped vehicles







dealers that sell and service the brand of vehicle. Examples include the following:– Honda —HDS or Master Tech







dealers that sell and service the brand of vehicle. Examples include the following:– Toyota —Techstream






groups:2. Aftermarket scan tools are designed to

function on more than one brand of vehicle. Examples include the following:– Snap-on (various models including the

MT2500 and Modis) OTC (various models including Pegasus, Genisys and Task Master)






groups:2. Aftermarket scan tools are designed to

function on more than one brand of vehicle. Examples include the following:– AutoEnginuity and other programs that use a

laptop or handheld computer for the display





• Diagnostic Procedure– Diagnosis steps usually include the

following:• STEP 1: Verify the fault, making sure that it

is in the antilock system and not caused by a fault in the base brakes.






following:• STEP 2: Retrieve any stored diagnostic

trouble codes.






following:• STEP 3: Perform detailed tests to find the

root cause.






following:• STEP 4: Verify the repair of the fault and

clear any stored diagnostic trouble codes.




CHART 107–1




CHART 107–1 (continued)




ABS SAFETY ABS SAFETY PRECAUTIONSPRECAUTIONS




ABS Safety PrecautionsABS Safety Precautions

1. Avoid mounting the antenna for the transmitting device near the ABS control unit.

2. Avoid mounting tires of different diameter than that of the original tires.

3. Never open a bleeder valve or loosen a hydraulic line while the ABS is pressurized. The accumulator must be depressurized.





4. If arc welding on a vehicle, disconnect all computers (electronic control modules) to avoid possible damage due to voltage spikes.

5. Do not pry against or hit the wheel speed sensor ring.





• Quick and Easy Wheel Speed Sensor Diagnosis– A fault in a wheel speed sensor (WSS) is a

common ABS problem– A quick and easy test that works on most

Bosch ABS systems (and perhaps others) involves the following steps:

• STEP 1: Hoist the vehicle safely.





• Quick and Easy Wheel Speed Sensor Diagnosis– A quick and easy test that works on most


• STEP 2: Turn the ignition on (engine off).







• STEP 3: Spin a tire by hand as fast as possible.







• STEP 4: The ABS amber warning light should come on, indicating that a speed was detected but not by all the wheel speed sensors.







• STEP 5: Turn the ignition off to reset the ABS warning light.







• STEP 6: Repeat the test on each of the remaining wheels.





• If any wheel fails to turn on the ABS light, carefully inspect the wheel speed sensor for proper resistance and the tone ring and wiring

• If the ABS light is on all the time and does not reset when the ignition is turned off, the problem is not caused by a wheel speed sensor

Halderman ch107 lecture

Technology

Transcript of Halderman ch107 lecture