ADT Chassis, Suspension & Brake Systems 3 — Questions and Answers
Question 1: Audi uses a 'steering angle sensor' (G85) for ESP operation. After replacing a steering rack, which calibration is required?
- Steering angle sensor zero-point calibration via VCDS/ODIS with front wheels centered (Correct answer)
- Wheel speed sensor replacement on all four corners
- Full four-wheel alignment before any calibration
- Yaw rate sensor replacement and calibration
Correct answer: Steering angle sensor zero-point calibration via VCDS/ODIS with front wheels centered
G85 must be re-zeroed with the steering wheel and wheels centered after any rack or steering component replacement so ESP has an accurate reference.
Question 2: A technician inspects Audi B8 A5 front lower control arm bushings. The front bushing shows radial cracking but the rear hydraulic bushing feels firm. What is the correct service decision?
- Replace both lower control arms as an axle set because handling geometry changes if only one side is renewed (Correct answer)
- Replace only the front bushing on the affected arm
- The radial cracks are cosmetic; only replace when bushing is physically separated
- Replace only the rear hydraulic bushing since it carries more load
Correct answer: Replace both lower control arms as an axle set because handling geometry changes if only one side is renewed
Audi recommends replacing control arms in axle pairs to maintain symmetric handling characteristics and avoid alignment variance side-to-side.
Question 3: During a brake job on an Audi with electric parking brake (EPB), in which sequence must caliper piston retraction be performed?
- Activate EPB service mode in VCDS/ODIS first, retract piston, install new pads, then reactivate EPB (Correct answer)
- Manually turn the piston clockwise while pressing it in without any scan tool
- Fully apply the EPB before pressing piston straight in with a cube tool
- Remove the EPB motor, press piston in, reassemble motor, calibrate
Correct answer: Activate EPB service mode in VCDS/ODIS first, retract piston, install new pads, then reactivate EPB
EPB-equipped Audi calipers require the electronic service mode to retract the lead-screw-driven piston safely without damaging the motor or seals.
Question 4: A technician finds a DTC for 'Wheel Speed Sensor Signal Implausible — Rear Left' on an Audi with quattro. All wheel speed sensors test good individually. What is the NEXT diagnostic step?
- Compare all four wheel speed signals simultaneously during a road test to detect ratio errors from incorrect tire sizes or ABS ring damage (Correct answer)
- Replace the rear left wheel speed sensor
- Replace the ABS control module
- Check brake pad thickness on the rear left corner
Correct answer: Compare all four wheel speed signals simultaneously during a road test to detect ratio errors from incorrect tire sizes or ABS ring damage
An 'implausible' signal fault often means the sensor is working but its output disagrees with the other three — caused by ABS ring damage, tire size mismatch, or excessive bearing play.
Question 5: On an Audi with electromechanical power steering (EPS), the steering torque sensor (G269) returns a fault. What symptom would the driver most likely report?
- Steering assist varies erratically or is absent, accompanied by a steering warning light (Correct answer)
- Vehicle pulls strongly to one side even on straight roads
- Brake pedal pulsation under moderate braking
- Vibration felt through the floorboard at highway speed
Correct answer: Steering assist varies erratically or is absent, accompanied by a steering warning light
G269 provides torque input to the EPS motor controller; a fault causes the system to reduce or disable assist and illuminate a warning.
Question 6: What is the purpose of the 'brake application test' step in an Audi ODIS brake bleed procedure?
- It cycles the ABS pump and solenoids to purge air trapped in the HCU internal circuits (Correct answer)
- It verifies pad-to-rotor contact is correct after caliper reassembly
- It measures residual brake pressure in the calipers
- It recalibrates the brake pressure sensor after bleeding
Correct answer: It cycles the ABS pump and solenoids to purge air trapped in the HCU internal circuits
The ODIS-guided brake application test commands the ABS module to open and close solenoids, flushing air from the HCU galleries that manual bleeding cannot reach.
Question 7: An Audi owner complains of a loud clunk from the front suspension when hitting potholes. Inspection reveals the front strut mount bearing is worn. What additional component should always be inspected at the same time?
- Strut mount bearing plate AND the coil spring for cracks, especially at upper and lower seats (Correct answer)
- Rear sway bar end links
- Rear shock absorber top mounts
- Front CV axle boots
Correct answer: Strut mount bearing plate AND the coil spring for cracks, especially at upper and lower seats
A failed strut mount bearing often causes abnormal spring movement, which can crack MacPherson spring coils at the seated ends.
ADT Chassis, Suspension & Brake Systems 3
Audi uses a 'steering angle sensor' (G85) for ESP operation.
After replacing a steering rack, which calibration is required?