NCT Case Analysis & Practical Application 3

Question 1

A technician is diagnosing a fleet vehicle that stalls at idle but runs fine at higher RPMs. Fuel pressure tests are within specification. What system should be inspected next?

Accepted Answer

Idle air control (IAC) valve or throttle body

Answer

A faulty IAC valve or dirty throttle body restricts the air bypassed around the throttle plate at idle, causing stalls despite normal fuel pressure.

Question 2

During a fleet vehicle inspection, the technician finds that the serpentine belt is cracked but not yet frayed. Company policy requires replacement only upon failure. What is the correct action?

Accepted Answer

Replace the belt immediately and document the deviation from policy with justification

Answer

A cracked serpentine belt presents an imminent failure risk that could strand the vehicle or disable the charging and cooling systems; replacement is the technically correct safety action and should be documented.

Question 3

A fleet technician encounters a diesel truck that has excessive black smoke from the exhaust under load. What is the FIRST system to evaluate?

Accepted Answer

Fuel injection system and air intake restriction

Answer

Black smoke under load in a diesel engine indicates an overly rich air-fuel mixture, most commonly caused by a restricted air intake or faulty fuel injection system delivering too much fuel.

Question 4

A fleet manager reviews telematics data and finds that one driver consistently shows hard braking events five times more often than peers on the same routes. What is the appropriate fleet management response?

Accepted Answer

Conduct a coaching session with the driver and monitor subsequent telematics data

Answer

Driver coaching using objective telematics data is the standard industry approach to correct unsafe driving behaviors before they result in accidents or excessive component wear.

Question 5

A fleet vehicle's OBDII scanner shows a P0420 code (Catalyst System Efficiency Below Threshold). Before condemning the catalytic converter, what should the technician verify?

Accepted Answer

Upstream and downstream O2 sensor operation and any exhaust leaks

Answer

A faulty upstream or downstream O2 sensor, or an exhaust leak between the sensors, can falsely trigger P0420 before the catalytic converter itself is at fault.

(NCT) NAFA Certified Technician Practice Test

(NCT) NAFA Certified Technician Practice Test

NCT Case Analysis & Practical Application 3