Exhaust Systems Specialist Flashcards

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

Answer: The catalytic converter may be failing

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

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

Answer: Heat can ignite or damage nearby flammable components

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

A P0420 diagnostic trouble code typically indicates what?

Answer: Catalyst efficiency below threshold (Bank 1)

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

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

Answer: Resonator

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

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

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

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

What is a common symptom of a severely clogged catalytic converter?

Answer: Loss of power and poor high-speed performance

A clogged converter restricts flow, causing power loss especially at higher engine speeds.

Why must a torque wrench be used when installing oxygen sensors and exhaust flange bolts?

Answer: To prevent thread galling and ensure proper sealing without distortion

Proper torque prevents thread damage, leaks, and flange distortion from over- or under-tightening.