Question 1

The PCM continuously tests the electrical integrity of the system and monitors the EGR flow rate twice per trip.

Accepted Answer

The PCM (Powertrain Control Module) does not specifically monitor the EGR (Exhaust Gas Recirculation) flow rate twice per trip. It continuously monitors various engine and vehicle operations, including the EGR system, but the frequency and specifics of EGR flow rate monitoring can vary based on the vehicle's design and the manufacturer's programming.

Question 2

Technician A says that a fuel-saturated evaporative emissions canister will cause negative STFT numbers. Technician B says that a fuel-saturated evaporative emissions canister will cause negative LTFT numbers. Who is correct?

Accepted Answer

A fuel-saturated evaporative emissions canister can cause both negative short-term fuel trim (STFT) and long-term fuel trim (LTFT) numbers due to the extra fuel vapors being introduced into the intake system, leading to a richer mixture.

Question 3

During the diagnostic test procedure for a catalyst efficiency code, a diagnostic scan tool is connected to the DLC with the vehicle at operating temperature, and the data screen displays the precatalyst oxygen sensor continually switching between 200 mV - 800 mV, while the postcatalyst oxygen sensor's output voltage stays relatively steady at 700 mV. Technician A says that the postcatalyst oxygen sensor is fixed rich and should be replaced. Technician B says that the oxygen sensor readings are both normal. Who is correct?

Accepted Answer

The precatalyst oxygen sensor should switch between 200 mV and 800 mV, indicating normal operation. The postcatalyst oxygen sensor should have a relatively steady reading if the catalyst is functioning properly, as it indicates the catalytic converter is effectively reducing emissions. Therefore, Technician B is correct.

Question 4

The heated oxygen sensor monitor will test all of the following EXCEPT:

Accepted Answer

The heated oxygen sensor monitor does not test the sensor light off temperature; it focuses on the performance of the sensor circuit, signal switch rate, and heater element.

Question 5

A vehicle is brought in for repair with the complaint of poor fuel economy. A diagnostic scan tool is attached to the DLC with the vehicle at operating temperature, and the technician determines that the precatalyst oxygen sensor voltage is biased high, the injector pulse width is long, and both STFT and LTFT are high. All of the following conditions could cause this EXCEPT:

Accepted Answer

High fuel pressure would cause the fuel trims to be negative, not positive.

Question 6

To determine the efficiency of the catalytic converters, the PCM uses a complex software program and data look-up tables when the catalyst monitor is run.

Accepted Answer

The Powertrain Control Module (PCM) indeed uses a complex software program and data look-up tables to determine the efficiency of the catalytic converters when the catalyst monitor is run. This process involves analyzing the input from various sensors, including the oxygen sensors before and after the catalytic converter, to ensure the converter is functioning properly and efficiently reducing emissions.

Question 7

The evaporative emissions system monitor will not run if the oxygen sensor monitor failed.

Accepted Answer

The evaporative emissions system monitor often requires the oxygen sensor monitor to have run and passed, as it relies on the oxygen sensor's data to accurately measure fuel vapor emissions. If the oxygen sensor monitor has failed, it can prevent the evaporative emissions system monitor from running.

Question 8

OBD II requires an EGR system monitor that will test all of the following EXCEPT:

Accepted Answer

EGR rpm effect is not directly tested by the OBD II system. OBD II focuses on monitoring the EGR's mechanical and electrical functions and flow rates to ensure emissions are within allowable limits, rather than the effect on engine rpm.

Question 9

If a fault is detected during two consecutive trips, the MIL is turned on, a DTC is set, and freeze-frame data is stored.

Accepted Answer

The answer of If a fault is detected during two...

Question 10

The EVAP charcoal canister functions as a storage container for fuel vapors.

Accepted Answer

The EVAP (Evaporative Emission Control System) charcoal canister captures and stores fuel vapors from the fuel tank and carburetor (if equipped) to prevent them from escaping into the atmosphere. These vapors are later purged and burned in the engine during certain operating conditions.

Question 11

Technician A says the heated oxygen sensor monitor performs two distinct tests; one test verifies the performance of the pre- and post-oxygen sensor heater element and circuit. Technician B says the heated oxygen sensor monitor performs two distinct tests; one test monitors the pre- and post-oxygen sensor signal switch rate and signal circuit. Who is correct?

Accepted Answer

Both Technician A and Technician B are correct. The heated oxygen sensor monitor indeed performs two distinct tests: one for verifying the performance of the oxygen sensor heater element and circuit (as mentioned by Technician A), and another for monitoring the oxygen sensor signal switch rate and signal circuit (as mentioned by Technician B). These tests ensure the oxygen sensors are heating properly and responding correctly to changes in the exhaust gas composition.

Question 12

The conventional oxidation catalyst is not capable of converting oxides of nitrogen (NO_X).

Accepted Answer

Conventional oxidation catalysts are designed to oxidize hydrocarbons and carbon monoxide, but they are not effective at reducing nitrogen oxides (NOx) to nitrogen and oxygen.

Question 13

An evaporative emissions system large leak or no purge flow could be caused by all of the following EXCEPT:

Accepted Answer

A loose or missing crankcase oil filler cap is not related to the evaporative emissions system, which deals with fuel vapors, not engine oil vapors.

Question 14

In order for the MIL to be extinguished, two consecutive good global trips must be seen by the PCM.

Accepted Answer

The MIL (Malfunction Indicator Lamp) typically requires three consecutive good trips to be extinguished, not two.

Question 15

Downstream secondary air injection systems are only used on conventional oxidation catalyst systems.

Accepted Answer

Downstream secondary air injection systems are used on both conventional oxidation catalyst systems and three-way catalyst systems.

Question 16

The enhanced system must be capable of detecting a leak as small as 0.060 inch (1.5 mm).

Accepted Answer

The answer of The enhanced system must be capable of...

Question 17

Technician A says the secondary air monitor tests for flow by monitoring the oxygen sensor response. Technician B says the secondary air monitor is run once per drive cycle. Who is correct?

Accepted Answer

The secondary air monitor tests for flow by monitoring the oxygen sensor response to verify if the secondary air injection system is working properly (Technician A is correct). It is typically run once per drive cycle to ensure the system's functionality without causing unnecessary load on the vehicle's processing unit (Technician B is correct).

Question 18

Technician A says that the EGR system monitors the ability of the fuel tank to hold pressure as well as the purge of vapors into the intake system. Technician B says that the EVAP system collects fuel vapors in the expansion cavity at the top of the fuel tank, then sends them to the charcoal canister. Who is correct?

Accepted Answer

Technician A is incorrect because the description given pertains to the EVAP (Evaporative Emission Control) system, not the EGR (Exhaust Gas Recirculation) system. Technician B is correct as the EVAP system is designed to capture fuel vapors from the fuel tank and store them in the charcoal canister until they can be purged and burned in the engine.

Question 19

Technician A says the catalyst's ability to store and release oxygen is a direct indication of the catalyst's performance. Technician B says the catalyst monitor compares the signal from both the upstream and downstream oxygen sensors. Who is correct?

Accepted Answer

Technician A is correct because the catalyst's ability to store and release oxygen affects its efficiency in converting harmful emissions. Technician B is also correct because the catalyst monitor does indeed compare signals from both the upstream and downstream oxygen sensors to assess the catalyst's performance.

Question 20

The EGR monitor is an intrusive test, and the customer may notice an rpm fluctuation while the test is taking place.

Accepted Answer

The EGR (Exhaust Gas Recirculation) monitor test can cause noticeable RPM fluctuations because it actively tests the EGR system's operation by opening and closing the EGR valve, which can affect engine speed.

Quiz 10: Strategies of on Board Diagnostic Non Continuous Monitors