Engine Performance & Diagnostics Flashcards

An EA888 2.0T sets P2015 (intake manifold runner position sensor range/performance). What is the most common cause?

Answer: A worn or broken intake manifold runner flap linkage or position sensor

Worn runner flap linkages or failed position sensors are a well-known cause of P2015 on these engines.

Which statement about short-term and long-term fuel trims is correct?

Answer: Positive trims mean the ECM is adding fuel to correct a lean condition

Positive trim values mean the ECM is adding fuel because the O2 feedback shows a lean mixture.

A customer reports that an EA888 Gen 1/early Gen 2 engine uses about 1 quart of oil per 1,000 miles with no visible leaks. What is a known cause on these engines?

Answer: A piston ring design that allows oil consumption

Early EA888 engines had a piston ring design that caused excessive oil consumption, which VW addressed with revised pistons and rings.

On a VW TSI engine with a low-pressure fuel sensor (G410) and a high-pressure sensor (G247), a cranks-but-runs-rough fault shows low pressure on G410 only. Where should diagnosis focus?

Answer: In-tank fuel pump, fuel pump control module, or filter

Low pressure on the supply side points to the in-tank pump circuit or a restriction before the high-pressure pump.

Which tool or procedure checks whether all OBD-II self-tests have finished after a repair?

Answer: Readiness monitor status

Readiness monitors show whether each emissions self-test has completed since codes were last cleared.

A narrowband pre-cat O2 sensor in closed loop on a healthy engine should normally switch between about which voltages?

Answer: 0.1 and 0.9 V

Zirconia narrowband sensors swing roughly 0.1 V (lean) to 0.9 V (rich) around stoichiometric.

In a leak-down test, bubbles appear in the coolant expansion tank. What does this suggest?

Answer: A head gasket leak or cracked head into a coolant passage

Combustion pressure getting into the cooling system means a breach between the cylinder and a coolant passage.