AUDI Vehicle Diagnostics 3 — Questions and Answers
Question 1: An Audi technician notices a P0171 (system too lean, bank 1) code. Which sensor failure would LEAST likely cause this code?
- Mass airflow sensor reading low
- Vacuum leak after the MAF
- Oxygen sensor stuck rich (Correct answer)
- Fuel pressure below specification
Correct answer: Oxygen sensor stuck rich
An oxygen sensor stuck in a rich reading would cause the ECU to add fuel, potentially resulting in a rich condition, not a lean fault code.
Question 2: During an Audi EVAP system diagnosis, a technician performs a smoke test and finds no visible leak. What is the next recommended step?
- Replace the charcoal canister
- Check the vent valve and purge valve operation with a scan tool (Correct answer)
- Replace the fuel cap
- Clear the code and retest
Correct answer: Check the vent valve and purge valve operation with a scan tool
If a smoke test reveals no physical leak, the vent valve or purge valve may be malfunctioning electrically, which can be verified with actuator tests on a scan tool.
Question 3: On an Audi with Haldex AWD (used in Q3/TT), which condition would cause the system to default to front-wheel drive only?
- Low fuel level
- Haldex oil pump failure or low fluid level (Correct answer)
- Tire pressure imbalance exceeding 5 PSI
- Yaw rate sensor fault
Correct answer: Haldex oil pump failure or low fluid level
The Haldex unit relies on an electric oil pump to pre-fill the clutch pack; pump failure or low fluid causes the system to default to FWD mode.
Question 4: A technician is diagnosing an Audi with a faulty variable valve timing (VVT) solenoid. Which symptom would be MOST consistent with this fault?
- Hard start when cold only
- Poor fuel economy and rough idle at all temperatures (Correct answer)
- Overheating at highway speeds
- ABS activation at low speeds
Correct answer: Poor fuel economy and rough idle at all temperatures
A failed VVT solenoid prevents proper camshaft phasing, leading to rough idle and reduced fuel efficiency across all operating temperatures.
Question 5: When using ODIS-E to diagnose an Audi SRS airbag fault, the technician finds a stored code for high resistance in the driver's airbag squib circuit. What is the correct diagnostic approach?
- Replace the airbag immediately
- Measure resistance of the squib circuit with the airbag disconnected using a dedicated squib resistance tool (Correct answer)
- Clear the code and retest three times
- Replace the airbag control module
Correct answer: Measure resistance of the squib circuit with the airbag disconnected using a dedicated squib resistance tool
A dedicated squib resistance tool measures the circuit without risking accidental deployment, safely identifying whether the fault is in the wiring or the squib itself.
Question 6: An Audi B9 A4 exhibits hesitation during acceleration. Long-term fuel trim (LTFT) is +18%. What does this value indicate?
- The engine is running rich and the ECU is reducing fuel
- The ECU is adding 18% more fuel than the base map to compensate for a lean condition (Correct answer)
- Fuel pressure is 18% above specification
- The oxygen sensor is reading 18% below normal
Correct answer: The ECU is adding 18% more fuel than the base map to compensate for a lean condition
A positive LTFT of +18% means the ECU is commanding 18% more fuel than the base map, indicating the engine is running lean and compensation is near its limit.
Question 7: Which Audi-specific feature in ODIS allows a technician to follow a structured diagnostic path guided by fault symptoms rather than individual codes?
- Adaptation channels
- Guided fault finding (GFF) (Correct answer)
- Basic settings menu
- Coding long codes
Correct answer: Guided fault finding (GFF)
Guided Fault Finding (GFF) in ODIS provides structured, symptom-based diagnostic procedures specific to the vehicle's configuration and detected faults.
AUDI Vehicle Diagnostics 3
An Audi technician notices a P0171 (system too lean, bank 1) code.
Which sensor failure would LEAST likely cause this code?