ASE Exhaust Systems Specialist 3

Question 1

A downstream oxygen sensor voltage switches rapidly like the upstream sensor. What does this indicate?

Accepted Answer

The catalytic converter may be failing

Answer

An efficient converter produces a steady downstream signal; rapid switching suggests reduced converter efficiency.

Question 2

When welding a new section of exhaust pipe, why should the technician avoid welding near rubber hangers and fuel lines?

Accepted Answer

Heat can ignite or damage nearby flammable components

Answer

Welding heat can melt rubber hangers and ignite fuel, so flammable components must be protected or removed.

Question 3

A P0420 diagnostic trouble code typically indicates what?

Accepted Answer

Catalyst efficiency below threshold (Bank 1)

Answer

P0420 signals the catalyst system efficiency on Bank 1 has dropped below the required threshold.

Question 4

Which exhaust component is specifically designed to cancel certain sound frequencies through wave interference?

Accepted Answer

Resonator

Answer

A resonator uses chamber geometry to cancel specific drone frequencies via wave interference.

Question 5

Before condemning a catalytic converter for a P0420 code, the technician should FIRST verify what?

Accepted Answer

There are no exhaust leaks and the O2 sensors are functioning correctly

Answer

Exhaust leaks and faulty O2 sensors can falsely trigger P0420, so they must be ruled out first.

ASE Practice Test