SMOG REPAIR TECH EXAM PREP 2025
QUESTIONS WITH 100% CORRECT
ANSWERS!!
1 of 54
Term
Two technicians are discussing the different types of catalytic
converters. There seems to be some confusion between "oxidizing ",
"reducing ", "dual-bed" and "three-way" catalytic converters. What
statement best describes the difference?
Give this one a try later!
Dual-bed converters are solely for Reducing converters enhance fuel
lean combustion efficiency
, Three way and/or dual bed
Oxidizing converters only reduce
catalectic converter's are both
emissions
oxidizing and reducing
Don't know?
2 of 54
Term
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?
Give this one a try later!
The burn time decreases with The burn time increases with engine
engine speed speed
The burn time is not affected The burn time is doubled as engine
by the engine speed. speed rises
Don't know?
3 of 54
Term
,A vehicle fails the smog check inspection for high HC. The vehicles
not PCM controlled. The technician checks the ignition system with
an ignition Oscilloscope. The third cylinder in the firing order has a
short upward slant on the spark line. The firing line is also well above
the 15kV line. What is the most likely cause of the emissions failure?
Give this one a try later!
None of the above (a small vacuum
leak would not be detected, the
Misfire on one cylinder
computer will automatically
compensate for it)
Vacuum leak affecting cylinder
Plugged in-line fuel filter
three
Don't know?
4 of 54
Term
A technician is using a digital storage oscilloscope to test the
performance of an oxygen sensor. The DSO is set to the 50ms per
division. The technician conducts a sap test and captures the freeze
frame. The frame measures three divisions for the O2 sensor voltage
dress from 175 MV to 800 MV. How will the technician interpret this
test result?
Give this one a try later!
, The O2 sensor responded in The O2 sensor detects less oxygen
150 MS and fails the test when the EGR valve is activated
The O2 sensor heater resistance is The TPS voltage is at reference
within specifications voltage
Don't know?
5 of 54
Term
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.
Give this one a try later!
The O2 sensor heater resistance is The O2 sensor detects less oxygen
within specifications when the EGR valve is activated
The air injection system is
The TPS voltage is at reference
staying in the "upstream"
voltage
mode at all times.
Don't know?
6 of 54
QUESTIONS WITH 100% CORRECT
ANSWERS!!
1 of 54
Term
Two technicians are discussing the different types of catalytic
converters. There seems to be some confusion between "oxidizing ",
"reducing ", "dual-bed" and "three-way" catalytic converters. What
statement best describes the difference?
Give this one a try later!
Dual-bed converters are solely for Reducing converters enhance fuel
lean combustion efficiency
, Three way and/or dual bed
Oxidizing converters only reduce
catalectic converter's are both
emissions
oxidizing and reducing
Don't know?
2 of 54
Term
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?
Give this one a try later!
The burn time decreases with The burn time increases with engine
engine speed speed
The burn time is not affected The burn time is doubled as engine
by the engine speed. speed rises
Don't know?
3 of 54
Term
,A vehicle fails the smog check inspection for high HC. The vehicles
not PCM controlled. The technician checks the ignition system with
an ignition Oscilloscope. The third cylinder in the firing order has a
short upward slant on the spark line. The firing line is also well above
the 15kV line. What is the most likely cause of the emissions failure?
Give this one a try later!
None of the above (a small vacuum
leak would not be detected, the
Misfire on one cylinder
computer will automatically
compensate for it)
Vacuum leak affecting cylinder
Plugged in-line fuel filter
three
Don't know?
4 of 54
Term
A technician is using a digital storage oscilloscope to test the
performance of an oxygen sensor. The DSO is set to the 50ms per
division. The technician conducts a sap test and captures the freeze
frame. The frame measures three divisions for the O2 sensor voltage
dress from 175 MV to 800 MV. How will the technician interpret this
test result?
Give this one a try later!
, The O2 sensor responded in The O2 sensor detects less oxygen
150 MS and fails the test when the EGR valve is activated
The O2 sensor heater resistance is The TPS voltage is at reference
within specifications voltage
Don't know?
5 of 54
Term
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.
Give this one a try later!
The O2 sensor heater resistance is The O2 sensor detects less oxygen
within specifications when the EGR valve is activated
The air injection system is
The TPS voltage is at reference
staying in the "upstream"
voltage
mode at all times.
Don't know?
6 of 54
