Exam 34: Emission Control Diagnosis and Service

Identify the causes of high HC emissions.

A vehicle is in the shop because it failed an emissions test due to excessive carbon monoxide (CO). The fault was a bad oxygen sensor that was easily replaced. Technician A says that the EGR system should be checked before the vehicle is retested. Technician B says the vehicle should be tested with a five-gas analyzer before it is retested. Who is correct?

Excessive oil consumption can be caused by a plugged PCV hose.

Another term for detonation is spark knock.

What can result from a charcoal canister saturated with gasoline?

The customer complains of a loss of power at highway speeds and a rough running engine at all speeds. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 700 ppm, CO = 0.2%, CO₂ = 9.2%, O₂ = 6.2%, and NO _X = 330 ppm. What is the most likely cause?

Which of the following emission systems is typically NOT controlled by the PCM?

While discussing catalytic converter diagnosis, Technician A says a delta temperature test should be conducted. Technician B says a good converter is evident by low amounts of CO₂ in the tailpipe exhaust. Who is correct?

Which of the following conditions may result from too little EGR flow?

An AIR system should be checked for overall efficiency by looking at the changes in exhaust quality when the system is turned on and off.

The first time the OBD-II system monitor detects a fault in the system, a ___________________ DTC is set. This will not cause the MIL light to illuminate and will self-erase if the monitor passes on the next trip.

Higher than normal ____________________ emissions may be caused by an overheated engine.

The exhaust analyzers used in I/M 240 measure the emissions levels in ppm.

Technician A says an I/M 240 test is four minutes long. Technician B says the test cycle includes acceleration, deceleration, and cruising on an actual road test. Who is correct?

During an I/M 240 test, the vehicle's exhaust is collected by a CVS system.

Some AIR systems will set a ___________________ in the PCM if there is a fault in the system.

A stuck open EGR valve could cause _____.

The customer complains of poor fuel economy. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 72 ppm, CO = 3.2%, CO₂ = 10.3%, O₂ = 0.2%, and NO _X = 122 ppm. What is the most likely cause?

Technician A says if the EGR valve does not open, the engine may emit excessive amounts of HC. Technician B says if the EGR valve does not open, the engine may detonate on acceleration. Who is correct?

A catalytic converter can be tested by measuring the inlet and outlet temperatures.