ADT Emissions Control & Environmental Compliance 3 — Questions and Answers
Question 1: An Audi Q7 3.0 TDI (EA897) enters limp mode after the AdBlue tank runs empty. How is full power restored after refilling?
- Perform a forced DPF regeneration
- Clear fault codes only — power restores automatically
- Reset the SCR adaptation via VCDS/OBD and clear codes after confirming fluid level (Correct answer)
- Replace the NOx sensor to reset the counter
Correct answer: Reset the SCR adaptation via VCDS/OBD and clear codes after confirming fluid level
After AdBlue refill, the SCR adaptation must be reset through diagnostic software and faults cleared before the ECU exits the power-reduction strategy.
Question 2: What does a negative fuel trim (LTFT) value at idle combined with a rich lambda reading typically indicate regarding emissions compliance?
- Lean mixture causing NOx increase
- Rich mixture causing elevated CO and HC emissions at the tailpipe (Correct answer)
- Normal closed-loop operation
- Faulty upstream oxygen sensor
Correct answer: Rich mixture causing elevated CO and HC emissions at the tailpipe
Negative LTFT means the ECU is subtracting fuel to compensate for a rich condition, and if trims are saturated, excess CO and HC will pass through the catalyst.
Question 3: During OBD II readiness monitor testing for an Audi, the oxygen sensor monitor shows 'not ready.' What driving cycle is most likely required to set it?
- A cold start followed by immediate highway driving
- Idle for 10 minutes
- A standard warm-up cycle with steady-state cruise then deceleration fuel cut-off (Correct answer)
- Multiple WOT acceleration events
Correct answer: A standard warm-up cycle with steady-state cruise then deceleration fuel cut-off
The O2 sensor monitor requires a warm engine, steady cruise to establish closed-loop, and deceleration fuel cut-off to test the sensor's lean response.
Question 4: What is the legally mandated maximum allowable venting of HFC-134a refrigerant during Audi A/C service under EPA Section 609?
- No venting is permitted; all refrigerant must be recovered (Correct answer)
- Up to 35 grams may be vented per service event
- Venting is permitted only if the charge is under 2 lbs
- Small releases under 1 oz are exempt
Correct answer: No venting is permitted; all refrigerant must be recovered
EPA Section 609 prohibits all intentional venting of refrigerants with global warming potential; technicians must recover refrigerant before opening any A/C system.
Question 5: An Audi 3.0 TFSI shows P2096 (post-catalyst fuel trim lean, bank 1). Which downstream sensor is providing this reading?
- Pre-catalyst wideband lambda sensor (G39)
- Post-catalyst narrowband oxygen sensor (G130) (Correct answer)
- NOx sensor downstream of TWC
- Exhaust gas temperature sensor
Correct answer: Post-catalyst narrowband oxygen sensor (G130)
The post-catalyst narrowband oxygen sensor (G130) monitors TWC efficiency; a lean signal triggers P2096 if the catalyst is consuming excess oxygen or the sensor is faulty.
Question 6: A California-specification Audi must meet which emissions standard that is stricter than Federal Tier 3 requirements?
- LEV III / SULEV30 (Correct answer)
- Euro 6d-TEMP
- OBD-II Stage 2
- NMHC Tier 4
Correct answer: LEV III / SULEV30
California's LEV III SULEV30 standard (Super Ultra Low Emission Vehicle) sets lower NOx and NMOG thresholds than Federal Tier 3 regulations.
Question 7: When an Audi's catalytic converter is contaminated by coolant intrusion, which exhaust gas reading changes most dramatically on a 4-gas analyzer?
- CO increases sharply
- CO2 drops significantly (Correct answer)
- NOx spikes
- O2 drops to zero
Correct answer: CO2 drops significantly
Coolant contamination poisons catalyst substrate, drastically reducing the conversion of CO to CO2, causing CO2 to drop and CO to rise simultaneously.
ADT Emissions Control & Environmental Compliance 3
An Audi Q7 3.0 TDI (EA897) enters limp mode after the AdBlue tank runs empty.
How is full power restored after refilling?