ASE L1

The correct answer is the EGR system. The EGR system, or Exhaust Gas Recirculation system, is responsible for reducing nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the engine's combustion chambers. This helps to lower the combustion temperature and reduce the formation of NOx gases. The catalytic converter also plays a role in reducing emissions, but it primarily focuses on converting harmful pollutants like carbon monoxide and hydrocarbons into less harmful substances. The PCV system (Positive Crankcase Ventilation) and EFE system (Early Fuel Evaporation) are not directly related to controlling nitrogen oxide emissions.

The first step in determining the cause of the problem when a customer complains that their vehicle lacks power would be to road test the vehicle. This involves taking the vehicle for a drive to observe its performance and behavior firsthand. By doing so, a technician can assess factors such as acceleration, engine responsiveness, and any abnormal noises or vibrations. This initial road test provides valuable information that can help narrow down potential causes and guide further diagnostic procedures.

The usual number of terminating resistors on a CAN harness is two. Terminating resistors are used to eliminate signal reflections and ensure proper signal transmission on a CAN bus. Placing a terminating resistor at each end of the bus helps to match the impedance of the bus and prevent signal distortion. Having two terminating resistors, one at each end, ensures optimal signal quality and reduces the risk of communication errors on the CAN network.

A zirconia oxygen sensor should respond to changes in the air/fuel ratio within 100 milliseconds. This means that once the sensor reaches its operating temperature, it is able to detect and react to changes in the air/fuel mixture within a relatively short period of time. This quick response time is important for the sensor to accurately measure the oxygen levels in the exhaust gases and provide feedback to the engine control unit for optimal fuel combustion.

A clogged EGR (Exhaust Gas Recirculation) supply tube can cause excessive NOx (nitrogen oxides) emissions in a composite vehicle. The EGR system is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce combustion temperatures and lower NOx emissions. If the supply tube is clogged, it can restrict the flow of exhaust gases into the intake manifold, leading to higher combustion temperatures and increased NOx emissions. Therefore, a clogged EGR supply tube could be causing the excessive NOx emissions observed in the failed I/M 240 test.

Technician B is correct. A hissing noise from the tailpipe during a cylinder leakage test indicates that there is a problem with the exhaust valve. This could be caused by a burnt exhaust valve, which would prevent it from sealing properly and allowing air to escape. Technician A's suggestion of a worn down cam lobe would not cause a hissing noise from the tailpipe. Therefore, only Technician B is correct in this scenario.

Oxides of Nitrogen begin to form when combustion temperatures exceed 2500° F. At this temperature, the high energy of the combustion process causes nitrogen and oxygen molecules in the air to react and form various nitrogen oxides, such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). These oxides of nitrogen are harmful pollutants that contribute to air pollution and can have negative effects on human health and the environment.

The default throttle position on the composite vehicle is set at 15%. This means that when the vehicle is started or the throttle is not being actively controlled, it will be positioned at 15% open. This allows for a small amount of power to be delivered to the engine, enabling the vehicle to idle or move at a slow speed without the need for constant acceleration input from the driver.

During a drive cycle on a composite vehicle, it is required to have the fuel tank between 1/4 and 3/4 full. This is important to ensure accurate testing and measurement of the vehicle's performance and emissions. Having the fuel tank within this range provides a consistent fuel level that allows for reliable data collection and analysis. It helps to eliminate any potential variations in performance that may occur due to different fuel levels.

Technician B is correct. A defective catalytic converter can cause high emissions without reducing performance. This is because a faulty converter may not efficiently convert harmful gases into less harmful substances, leading to increased emissions. However, the converter's impact on performance may vary depending on the specific issue with the converter.

The GCWR (Gross Combined Weight Rating) is not typically entered into the computer prior to performing an I/M (Inspection and Maintenance) test. The GCWR refers to the maximum allowable weight of a fully loaded vehicle and its trailer, and it is not directly related to emissions or engine performance. The other options - emissions equipment, VIN (Vehicle Identification Number), and engine size - are commonly entered into the computer as they provide important information for conducting the I/M test.

The Immobilizer Module is responsible for verifying the key code, disabling injectors if the keycode is invalid, and recognizing the ECM ID number. However, it does not directly stop the operation of the starter motor.

Technician A is correct. A faulty catalytic converter can cause high emissions and trigger the Malfunction Indicator Light (MIL) to illuminate. The varying voltage of the downstream oxygen sensor, consistent with the upstream oxygen sensors, indicates that the catalytic converter may not be functioning properly. Technician B's suggestion that the downstream oxygen sensor could be defective does not explain the high emissions and illuminated MIL.

Both Technician A and Technician B are correct.
Technician A is correct because if the PCV valve is replaced with the wrong type, it can cause an imbalance in the air-fuel mixture, resulting in a higher idle speed.
Technician B is also correct because a leaking throttle body gasket can cause a vacuum leak, which can lead to a higher idle speed.
Therefore, both technicians are correct in their explanations for the high idle speed on an engine with a speed density fuel injection system.

A kinked vacuum line to the fuel pressure regulator can restrict the flow of fuel to the engine, leading to poor fuel economy. When the fuel pressure is not regulated properly, the engine may receive less fuel than required, resulting in decreased efficiency and increased fuel consumption. This can lead to lower mileage and higher fuel costs.

Both Technician A and Technician B are correct. A faulty TCC solenoid can indeed cause a vehicle with multiport fuel injection to stall on deceleration. The TCC solenoid is responsible for engaging and disengaging the torque converter clutch, and if it is faulty, it may not disengage properly, causing the engine to stall. Additionally, a contaminated throttle body can also cause stalling on deceleration. If the throttle body is dirty or clogged, it can restrict the airflow to the engine, leading to stalling. Therefore, both Technician A and Technician B are correct in their assessment of the potential causes of the problem.

An open circuit at pin B of the A/C pressure sensor, an open circuit at pin A of the A/C pressure sensor, and an open circuit at pin 5 of the ECM will all disable the air conditioner compressor clutch on the composite vehicle. However, a shorted A/C request switch will not disable the clutch as it will constantly send a signal to engage the compressor.

Both Technician A and Technician B are correct. A loose timing chain can cause the ISC motor to toggle back and forth at closed throttle, as it can affect the timing of the engine. Additionally, a worn distributor shaft gear can also cause this issue, as it can affect the accuracy of the rpm signal generated by the sensor inside the distributor. Therefore, both possibilities should be considered when diagnosing the problem.

The EGR valve not seating could be the root cause of the problem because an improperly seated EGR valve can cause an unstable idle and trigger a random misfire. The EGR valve is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce emissions. If the valve is not seating properly, it can disrupt the air-fuel mixture and cause misfires. This can also trigger the MIL (Malfunction Indicator Lamp) to turn on and store a DTC (Diagnostic Trouble Code) P0300 for a random misfire.

Technician A is correct. An open circuit to the ECM (Engine Control Module) pin 27 could indeed be a possible cause of the A/C clutch being inoperable. This is because ECM pin 27 likely controls the signal to the A/C clutch relay, and if there's an open circuit, the signal won't reach the relay, preventing the clutch from engaging.

Technician B's suggestion that a refrigerant leak could be the cause of the A/C clutch issue is not directly related to the electrical circuit problem described by Technician A, so Technician B's statement is not relevant to the given scenario.

The correct answer is in the ECM and the Instrument Cluster. CAN terminating resistors are used to prevent signal reflections and ensure proper communication in a CAN network. In this case, the terminating resistors are located in both the ECM (Engine Control Module) and the Instrument Cluster of the composite vehicle. This means that these two components have the necessary circuitry to terminate the CAN bus and maintain signal integrity.

The CO failure masked the NOx problem means that the high levels of carbon monoxide emissions were covering up the fact that there was also a problem with excessive nitrogen oxide emissions. This means that when the cause of the high carbon monoxide was fixed and the vehicle was retested, the true issue with the excessive NOx became apparent and caused the subsequent failure.

The correct answer is 8.25kΏ. The secondary winding of the ignition coils should have a resistance within the specified range. The reading of 8.25kΏ falls within this range, indicating that the secondary winding is functioning properly.

A poor connection at ECM terminal 12 can cause the composite vehicle to fail a loaded mode I/M test for excessive hydrocarbons. This poor connection may disrupt the communication between the ECM and other components, leading to incorrect fuel mixture and increased hydrocarbon emissions.

Technician B is correct. Excessive intake valve deposits can lead to incomplete combustion and higher NOx emissions. A restricted air filter, on the other hand, can affect the air-fuel mixture, but it is less likely to cause excessive NOx emissions. Therefore, Technician B's explanation is more relevant to the given scenario.

The shift solenoid No. 1 engaged is not required to engage the Torque Converter Clutch. The Torque Converter Clutch is typically engaged when the vehicle is in 3rd or 4th gear, the transmission temperature is at 150° F, and the vehicle speed is over 40 MPH. The shift solenoid No. 1 is responsible for controlling the shift between 1st and 2nd gear, but it is not directly related to the engagement of the Torque Converter Clutch.

If the EFE (Early Fuel Evaporation) heater stays energized all the time on an engine with TBI (Throttle Body Injection), it means that the heater will be continuously heating the fuel mixture, even when the engine is cold. This continuous heating will ensure that the engine gets a rich fuel mixture, which is beneficial for cold start conditions. Therefore, poor cold driveability would not be associated with this condition, as the continuous heating of the fuel mixture would actually improve the engine's performance during cold starts.

The most likely cause of the fuel pressure dropping to zero immediately after the pump stops running is a faulty regulator. The regulator is responsible for maintaining a consistent fuel pressure by controlling the flow of fuel returning to the fuel tank. If the regulator is faulty, it may not be able to properly regulate the fuel pressure, causing it to drop to zero when the pump stops running.

Performing a vacuum draw test is the most effective way to test the PCV system. This test involves using a vacuum gauge to measure the amount of vacuum being drawn by the system. By connecting the gauge to the PCV valve, any leaks or blockages in the system can be detected. This test provides a more comprehensive assessment of the PCV system's functionality compared to the other options listed.

The given CKP waveform shows a clear irregularity in the pattern, indicating that there is a chipped tooth on the reluctor. This irregularity can cause incorrect readings from the CKP sensor, leading to faulty engine timing and performance. Therefore, the correct answer is "The reluctor has a chipped tooth."

Technician A is correct. A flashing MIL (Malfunction Indicator Lamp) indicates a severe misfire that can cause damage to the catalytic converter. A broken circuit to ECM (Engine Control Module) pin 9 can disrupt the communication between the ECM and the ignition system, leading to a misfire. Technician B's suggestion of an open fuse number 4 is not relevant to the issue of a flashing MIL and poor running condition.

Technician A is correct. The fact that the vehicle only starts with the throttle held open suggests that the idle air control valve (IAC valve) may be stuck in the fully extended position. The IAC valve is responsible for regulating the closed throttle RPM in a multi-port fuel injection system. If it is stuck, it can prevent the vehicle from starting properly. Technician B's suggestion of a clogged fuel filter is not relevant to the given symptom of the vehicle only starting with the throttle held open.

Technician A is correct because a clogged catalytic converter can cause a lack of power in the vehicle. The scan data shows that the Bank 1 and Bank 2 Short Term Fuel Trim (STFT) values are both negative, indicating that the engine is running rich. This could be a result of a clogged catalytic converter, as it can restrict the exhaust flow and cause the engine to run inefficiently. Technician B's suggestion of low fuel pressure does not align with the provided scan data, as there are no indications of fuel pressure issues.

An EGR valve stuck closed would not cause an increase in hydrocarbon emissions. The EGR valve is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce the formation of nitrogen oxides (NOx). If the valve is stuck closed, it would prevent the recirculation of exhaust gases, but it would not directly contribute to increased hydrocarbon emissions.

Technician B is correct. A faulty secondary air system can cause backfiring. However, Technician A is incorrect in stating that if the hot air hose is missing on an engine with a thermostatic air cleaner, NOx emissions will be higher than normal.

Both Technician A and Technician B are correct. An engine with DI (Direct Ignition) ignition becomes harder to start as the outside temperature drops because lower temperatures can affect the performance of the ignition system. Technician A suggests that a faulty ignition coil could be the problem, which is a plausible explanation as a faulty coil can lead to weak or no spark, making it difficult for the engine to start. Technician B suggests that the coil wire may be bad, which is also a valid possibility as a damaged or worn-out coil wire can result in a weak or intermittent spark, causing starting issues. Therefore, both technicians are correct in their assessments.

Technician A is correct. The composite vehicle stalls when shifted into a drive range and immediately restarts, indicating a problem with the wire to pin 72 of the TCM being shorted to ground. This short circuit could be causing the stall and immediate restart. Technician B's suggestion of an open fuse 72 does not explain the symptoms described.

Both Technician A and Technician B are correct. A DTC P0420 code indicates low catalyst efficiency, which can be caused by multiple factors. Technician A is correct in suggesting that worn valve guide seals could be a potential root cause of the problem. These seals can allow oil to enter the combustion chamber, leading to increased emissions and decreased catalyst efficiency. Technician B is also correct in suggesting that a leaking exhaust system could trigger the DTC. A leak in the exhaust system can cause abnormal readings from the oxygen sensors, leading to a false low catalyst efficiency code. Therefore, both technicians are correct in their assessments.

Based on the given information, the waveform captured from the Bank 1 O2 sensor on the composite vehicle indicates that the sensor is functioning properly.

A poor connection at ECM terminal 36 could be the cause of the illuminated MIL and stored DTC for an EVAP system failure. A poor connection at this terminal could result in a loss of communication or faulty signals between the ECM (Engine Control Module) and the EVAP system components. This could lead to the MIL (Malfunction Indicator Lamp) being illuminated and a DTC (Diagnostic Trouble Code) being stored in the system, indicating a failure in the EVAP system.

The vehicle failed the low-speed portion of the two-speed idle test because the EGR valve is not seating properly. This means that the EGR valve is not closing properly during idle, causing an excessive amount of exhaust gas to enter the combustion chamber. As a result, the levels of HC (hydrocarbons) and CO (carbon monoxide) in the exhaust are higher than the allowed limits. The other options (clogged PCV valve, faulty pressure regulator, restricted fuel return line) do not directly affect the EGR valve or the levels of HC and CO in the exhaust.

Technician B is correct. The use of two throttle position sensors in a composite vehicle allows for a more accurate measurement of throttle position. Having two sensors provides redundancy, ensuring that if one sensor fails, the other can still provide accurate data. This redundancy improves the reliability and safety of the vehicle's throttle system. Technician A's statement about the failsafe in case one sensor fails is incorrect as it does not accurately explain the purpose of having two sensors.

The Comprehensive Component Monitor (CCM) is not a one-trip test; it monitors all components and systems that provide input or receive output signals from the powertrain control module (PCM) continuously while the vehicle is running. The other statements are correct: the Fuel Control, O2 Sensor, and Misfire Monitors run continuously, the EVAP Monitor will not run if the engine temperature is above 94 degrees F (34 degrees C), and a Long Term Fuel Trim (LTFT) reading of -30% could cause the Fuel Control Monitor to fail.

Neither Technician A nor Technician B is correct. The given information does not indicate that the system is stuck in the clear flood mode. Additionally, while a faulty MAP sensor can cause a no-start condition, there is no evidence in the provided data to suggest that the MAP sensor is the cause of the issue. Therefore, both technicians' explanations are incorrect.

Technician A is correct. A faulty intake cam position solenoid can indeed cause poor performance in a composite vehicle. The intake cam position solenoid is responsible for controlling the timing of the intake valves, which affects the engine's performance. If the solenoid is faulty, it may not be able to properly regulate the timing, leading to poor performance. On the other hand, Technician B's statement about the faulty exhaust cam position solenoid is not relevant to the given situation and does not address the issue of poor performance.

Based on the given readings, all of the symptoms listed (lack of power, rough idle, hard start) are consistent with the test results except for high CO emissions. CO emissions are typically high when there is incomplete combustion of fuel, which can be caused by factors such as a rich fuel mixture or a faulty oxygen sensor. However, the pressure drop readings for all the injectors are within the specified range of 21-24 psi, indicating that the injectors are balanced and delivering the correct amount of fuel. Therefore, high CO emissions would not be expected in this scenario.

Technician B is correct. Using a spark tester is a more effective way to test the ignition system. The snap throttle test is not specifically designed to evaluate ignition system performance, but rather to evaluate the response of the engine's air/fuel mixture to sudden changes in throttle position. A spark tester, on the other hand, directly checks for the presence of spark in the ignition system, providing a more accurate assessment of its performance.

Both Technician A and Technician B are correct. An engine misfire can result in low CO (carbon monoxide) readings because when a misfire occurs, the fuel is not burned completely, leading to a decrease in CO emissions. Additionally, a lean mixture, which refers to an insufficient amount of fuel in the air-fuel mixture, can also cause low CO and high O2 (oxygen) readings.

The correct answer is "an open circuit at pin 10 of the ECM." This is because an open circuit at pin 10 of the ECM would not directly affect the firing of cylinder number 4. However, an open circuit at pin 11 or pin 41 of the ECM could disrupt the ignition system, and a faulty ignition coil could also cause misfiring.