Vehicle: 2015 Audi Q7 Quattro (4LB), V6-3.0L SC (CTWA), Automatic transmission/transaxle

Mileage: 144,901

Problem: The owner brought his Quattro to the shop because the malfunction indicator light (MIL) was on. He mentioned that the idle is a little rough, but the car seemed to drive okay otherwise.

Case Details: After a brief test drive, the tech brought the car in the shop and connected a scan tool. He found diagnostic trouble code (DTC) P0018 – Crankshaft Position to Camshaft Position Correlation (Bank 2 Sensor A).

Because the owner needed the car back ASAP, the technician decided to call ALLDATA Tech-Assist for some diagnostic assistance. The Tech-Assist consultant recommended checking the engine oil level and condition first. If the oil was okay, he recommended swapping the bank 1 and bank 2 camshaft timing solenoids to see if the DTC followed.

The consultant also mentioned using the scope to check the camshaft/crankshaft correlation. DTC P0018 could be caused by a stretched timing chain. NOTE: When checking for a stretched timing chain, instead of spending a ton of time removing a valve cover or the front timing cover to see the timing marks, use a scope to capture the waveform patterns from the camshaft and crankshaft sensors. This diagnostic approach can also help diagnose circuit and sensor problems.

The technician checked the easiest thing first, the engine oil. Sure enough, the oil was low and dirty.

Confirmed Repair: He performed an oil and filter service, cleared the DTC and road-tested the Audi again. This time, the engine idled smooth, the MIL stayed off and there were no further issues. Fixed!