Vehicle: 2015 Audi Q5 Quattro (8RB) L4-2.0L Turbo (CPMB), Flex Fuel, Automatic Transmission/Transaxle

Mileage: 108,846

Problem: The customer stated that the malfunction indicator light was on and the engine was intermittently stalling.

Case Details: After connecting a scan tool, the technician scanned for diagnostic trouble codes (DTCs) and found P2177 - System Too Lean Off Idle Bank 1.

He smoke-tested the intake system and found no leaks. Next, he checked the crankcase vent valve, the mass airflow (MAF) sensor and the O2 sensors. All were within specifications. The fuel trims were normal at idle and under load. The alcohol content percentage was 8%.

The technician noticed that if he cleared the DTC and went on a test drive, the DTC and stalling issue would come back after about 10 miles.

While checking the scan tool’s live data, he found that the current fuel type in the system was ethanol, so he called the customer, who stated that he only uses 91 octane premium gas. Great clue! He followed ALLDATA’s test procedure for fuel quality sensor diagnosis and found that the sensor was defective

Confirmed Repair: The technician replaced the fuel quality sensor and cleared the DTC. A good test drive confirmed that the problem was repaired. Interesting fix!