REPAIR TECH EXAM PREP QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS
A PCM controlled vehicle fails the ASM smog test at both the 50/15 and 25/35 modes. the reason for the
failure is elevated carbon monoxide (CO) emissions at both portions of the test. The 02 sensor signal
voltage is always low. All other sensors are within specifications. What is the condition that causes the
emissions failure. - ANSWER - The air injection system is staying in the "upstream" mode at all times.
The 4-Gas readings shown in figure 3( high HC and O2 and low CO2) were recorded at idle with one
spark plug wire shorted to ground. The engine was at normal operating temperature. What is the
condition that best describes the 4-gas readings? - ANSWER - The catalytic converter is not functioning
properly anymore
The air fuel mixture entering the combustion chamber on an engine running at normal operating
temperature and load is 14.7:1. This makes sure burns in 1/3000 of a second. As the engine speed
increases, what happens to this burn time? - ANSWER - The burn time is not affected by the engine
speed.
A vehicle is in for a smog check and fails the tailpipe portion of the test. The vehicle is computer
controlled and has datastream available. When the technician scans the vehicle with KOEO, all the
sensor readings (voltage) A too high pain what is the cause of this condition - ANSWER - The computer
ground has too much resistance
Referring to figure 4 (one elevated firing line) what does the high spike represent? - ANSWER - The
voltage required that ionize the wireless gap in the circuit
A computer control vehicle has failed to tail pipe portion of a two speed idle smog check. The reason for
the failure is high carbon monoxide emissions at the 2500 RPM portion of the test only. What is most
likely the cause of this failure? - ANSWER - The vapor canister is fuel saturated
A vehicle is in the shop with a "no start" condition. The customer states of the vehicle has not been
running well lately. Spark and compression are tested and both are found to be within specifications.
Using a digital millimeter set to the vote scale technician probes to go inside of an injector and find the
, voltage reading stays the same what cranking the engine. what could be the cause of the no start
condition - ANSWER - The TPS voltage is at reference voltage
The technician suspect a leaking head gasket on a vehicle is being tested for a rough running condition.
An exhaust gas analyzer probe is placed just above the filler neck of the radiator, while the engine is
running. Which of the exhaust gases detective by the gas analyzer the best indicator of a leaking head
gasket - ANSWER - CO only
The maximum allowable voltage deviation between the height of firing lines of the spark plugs, as
viewed on the ignition oscilloscope is - ANSWER - 3000V
Assuming that the spark plug wire has been removed from cylinder #2 and shorted to ground what will
the resulting short voltage spike represent - ANSWER - The voltage necessary to overcome the rotor gap
in the distributor
When using a DVOM, The meter reads 1.234 Ohms while on the 2M scale. what is the actual reading? -
ANSWER - 1,234,000 ohms
An OBDI vehicle fails the ASM test for High HC at both the 50/15 and 25/25 portions of the test. The five
gas analysis shows low-carbon monoxide, high hydrocarbons, Low carbon dioxide, and elevated oxides
of nitrogen and oxygen emissions. When a metered amount of propane is introduced, carbon monoxide
emissions increase in HC and NOx decrease. What is most likely cause - ANSWER - The brake booster
diaphragm is ruptured
On a computer control and multiport fuel injection engine there are three ways for air to enter the
engine these are: - ANSWER - PCV, IAC, and throttle plate
What is the correct set up to conduct a proper compression test - ANSWER - Throttle open, ALL plugs
removed, and engine at operating temperature
A vehicle is in for a rough running condition. The customer has authorized a diagnosis. The technician is
checking the signal from the distributor with a DSO. The vehicle is using a Hall effect switch system in
the distributor to create the signal for the ignition control model module. What type of signal should the
technician see on the scope of the engine is in increase in RPM - ANSWER - a square wave signal that
increases in frequency as the engine speed increases
WITH COMPLETE SOLUTIONS
A PCM controlled vehicle fails the ASM smog test at both the 50/15 and 25/35 modes. the reason for the
failure is elevated carbon monoxide (CO) emissions at both portions of the test. The 02 sensor signal
voltage is always low. All other sensors are within specifications. What is the condition that causes the
emissions failure. - ANSWER - The air injection system is staying in the "upstream" mode at all times.
The 4-Gas readings shown in figure 3( high HC and O2 and low CO2) were recorded at idle with one
spark plug wire shorted to ground. The engine was at normal operating temperature. What is the
condition that best describes the 4-gas readings? - ANSWER - The catalytic converter is not functioning
properly anymore
The air fuel mixture entering the combustion chamber on an engine running at normal operating
temperature and load is 14.7:1. This makes sure burns in 1/3000 of a second. As the engine speed
increases, what happens to this burn time? - ANSWER - The burn time is not affected by the engine
speed.
A vehicle is in for a smog check and fails the tailpipe portion of the test. The vehicle is computer
controlled and has datastream available. When the technician scans the vehicle with KOEO, all the
sensor readings (voltage) A too high pain what is the cause of this condition - ANSWER - The computer
ground has too much resistance
Referring to figure 4 (one elevated firing line) what does the high spike represent? - ANSWER - The
voltage required that ionize the wireless gap in the circuit
A computer control vehicle has failed to tail pipe portion of a two speed idle smog check. The reason for
the failure is high carbon monoxide emissions at the 2500 RPM portion of the test only. What is most
likely the cause of this failure? - ANSWER - The vapor canister is fuel saturated
A vehicle is in the shop with a "no start" condition. The customer states of the vehicle has not been
running well lately. Spark and compression are tested and both are found to be within specifications.
Using a digital millimeter set to the vote scale technician probes to go inside of an injector and find the
, voltage reading stays the same what cranking the engine. what could be the cause of the no start
condition - ANSWER - The TPS voltage is at reference voltage
The technician suspect a leaking head gasket on a vehicle is being tested for a rough running condition.
An exhaust gas analyzer probe is placed just above the filler neck of the radiator, while the engine is
running. Which of the exhaust gases detective by the gas analyzer the best indicator of a leaking head
gasket - ANSWER - CO only
The maximum allowable voltage deviation between the height of firing lines of the spark plugs, as
viewed on the ignition oscilloscope is - ANSWER - 3000V
Assuming that the spark plug wire has been removed from cylinder #2 and shorted to ground what will
the resulting short voltage spike represent - ANSWER - The voltage necessary to overcome the rotor gap
in the distributor
When using a DVOM, The meter reads 1.234 Ohms while on the 2M scale. what is the actual reading? -
ANSWER - 1,234,000 ohms
An OBDI vehicle fails the ASM test for High HC at both the 50/15 and 25/25 portions of the test. The five
gas analysis shows low-carbon monoxide, high hydrocarbons, Low carbon dioxide, and elevated oxides
of nitrogen and oxygen emissions. When a metered amount of propane is introduced, carbon monoxide
emissions increase in HC and NOx decrease. What is most likely cause - ANSWER - The brake booster
diaphragm is ruptured
On a computer control and multiport fuel injection engine there are three ways for air to enter the
engine these are: - ANSWER - PCV, IAC, and throttle plate
What is the correct set up to conduct a proper compression test - ANSWER - Throttle open, ALL plugs
removed, and engine at operating temperature
A vehicle is in for a rough running condition. The customer has authorized a diagnosis. The technician is
checking the signal from the distributor with a DSO. The vehicle is using a Hall effect switch system in
the distributor to create the signal for the ignition control model module. What type of signal should the
technician see on the scope of the engine is in increase in RPM - ANSWER - a square wave signal that
increases in frequency as the engine speed increases
