402e Air ABS Diagnosis Flashcards
Explain the first step in troubleshooting an antilock brake system.
If at all possible, speak directly with the operator in order to get accurate firsthand information about the perceived ABS problem. At a minimum, review the customer and/or service advisor’s comments on the work order.
Identify the three (3) areas involved in a pre-check of the basic service brake system.
- brake adjustment
- condition of mechanical components
- air system operation
Identify the three (3) areas involved in a pre-check of the antilock brake system.
- integrity of connections
- physical damage
- use of tires of unequal sizes
The condition, security and integrity of the electrical cables and connections used on the antilock brake system are areas most likely to cause antilock brake system problems.
T/F
true
What other technical resource do you have if you are unable to determine the cause of an ABS system problem?
Accessing specialized technical support service staff is an option that is available through most ABS manufacturers.
Basic ABS diagnostics typically involves the use of what?
2
- built-in diagnostic equipment on the truck or trailer.
- appropriate ABS and/or vehicle service manuals.
Identify the types of diagnostic equipment that is typically used to access advanced fault codes.
Advanced fault codes are usually accessed by a hand-held scan tool that is equipped with a specific ABS diagnostic cartridge. A laptop computer that has appropriate ABS diagnostic software installed can also retrieve advanced fault codes.
The condition of an ABS indicator/warning light is first checked as part of a daily bulb check process.
T/F
true
Checking the condition of the wiring harness and associated connections is often done with an ohmmeter. What safety precautions should be part of the test process? (4)
- Ensure power to the system is OFF.
- Set the ohmmeter for the applicable scale.
- Use the appropriate ABS service manual to identify the specific test pins/sockets.
- Compare test readings with specific ABS component specifications.
The resistance value of each wheel speed sensor and integral electrical cable can be checked with an ohmmeter. The overall circuit resistance (wheel speed sensor, integral cable and cable to the ECU connector) can also be checked with an ohmmeter.
T/F
true
Increased wheel bearing wear and consequent increase in end play, has no effect on the position of the tone ring in relation to the wheel speed sensor.
T/F
false
The modulator valve may be affected by problems within the ABS electrical system as well as problems within the vehicle service brake air system.
T/F
true
In order to definitely identify an ECU or ECU/modulator valve as a defective item, advanced ABS diagnostic equipment should be used.
T/F
true
An electrical/electronic component can be readily exchanged if it is later found that the component is not defective.
T/F
false
Diagnosing an ABS system problem often starts when the ABS indicator/warning light is activated.
T/F
true
