ADT Chassis, Suspension & Brake Systems 2 — Questions and Answers
Question 1: An Audi with adaptive air suspension (CDC) shows a fault code for the front right shock absorber control. What is the most likely cause?
- Failed CDC valve inside the damper unit (Correct answer)
- Low air pressure in the reservoir
- Faulty level sensor at that corner
- Corroded wheel speed sensor signal
Correct answer: Failed CDC valve inside the damper unit
CDC faults specific to one damper typically point to the continuously variable damping valve integrated inside that shock absorber unit.
Question 2: When bleeding Audi electro-hydraulic brakes (e.g., SQ7 integrated braking system), which special procedure is required compared to conventional systems?
- The brake actuator must be cycled via VCDS to move fluid through internal solenoid circuits (Correct answer)
- Only the front calipers require bleeding
- Brake fluid must be pre-heated to 60°C before bleeding
- The parking brake must be fully applied throughout the bleed procedure
Correct answer: The brake actuator must be cycled via VCDS to move fluid through internal solenoid circuits
Integrated brake systems contain solenoid-controlled internal circuits that trap air unless cycled through dealer-level software such as VCDS or ODIS.
Question 3: A technician measures lateral runout on an Audi front rotor and finds 0.12 mm. The factory spec is 0.07 mm max. What is the BEST first corrective action?
- Index the rotor to a different stud position and re-measure (Correct answer)
- Immediately replace the rotor
- Machine the rotor on-car with an on-car lathe
- Replace the wheel hub bearing assembly
Correct answer: Index the rotor to a different stud position and re-measure
Re-indexing the rotor 1–2 stud positions often reduces runout caused by hub face irregularities before more invasive repairs are needed.
Question 4: On Audi vehicles with torque vectoring (sport differential), what braking-related interaction must a technician consider during brake service?
- The sport differential can apply individual rear brake pressure for yaw control, affecting pedal feel testing (Correct answer)
- The sport differential locks the rear axle, requiring extra bleeding ports
- Brake fluid must be DOT 5 silicone in sport differential-equipped vehicles
- The ABS module must be removed before rear caliper replacement
Correct answer: The sport differential can apply individual rear brake pressure for yaw control, affecting pedal feel testing
The sport differential uses hydraulic clutch packs and can interact with ESP torque vectoring braking, so road-test pedal feel should be verified after service.
Question 5: During a four-wheel alignment on an Audi B9 A4, the rear camber is within spec but rear toe is excessively toed-out on one side. Which component is MOST likely bent or worn?
- Rear toe link (inner or outer eccentric) (Correct answer)
- Rear upper control arm (Querlenker)
- Rear trailing arm bushings
- Rear subframe mounting bolt
Correct answer: Rear toe link (inner or outer eccentric)
On B9 Audi platforms, rear toe is set by the toe link with eccentric adjusters; damage or worn bushings at that link cause toe deviation.
Question 6: A customer reports an intermittent brake pedal that sinks slowly to the floor under steady pressure but braking performance feels normal otherwise. What is the MOST likely fault?
- Internal bypass in the master cylinder past worn primary cup seals (Correct answer)
- Air in the ABS modulator
- Warped front brake rotors
- Sticking caliper slide pins on both front calipers
Correct answer: Internal bypass in the master cylinder past worn primary cup seals
A slowly sinking pedal under steady pressure with normal dynamic braking is the classic symptom of internal master cylinder seal bypass.
Question 7: On an Audi Q7 with air suspension, the vehicle sits at the correct static height but the compressor runs excessively. What is the MOST likely diagnosis?
- Slow air leak in a bellows or solenoid valve keeping the compressor cycling to maintain pressure (Correct answer)
- Faulty height sensor sending false low signals
- Blocked air dryer causing false pressure buildup
- Failed ECU commanding continuous compressor operation
Correct answer: Slow air leak in a bellows or solenoid valve keeping the compressor cycling to maintain pressure
Excessive compressor run time with correct static height indicates a slow leak the compressor can continually compensate for rather than a sensor or control fault.
ADT Chassis, Suspension & Brake Systems 2
An Audi with adaptive air suspension (CDC) shows a fault code for the front right shock absorber control.
What is the most likely cause?