California Smog Check Inspector
Examination with Practice Questions And
Correct Answers (
1. A 2005 model-year vehicle arrives for a biennial Smog Check. The OBD II system
shows readiness monitors: Catalyst 'Not Ready', EVAP 'Ready', O2 Sensor 'Ready'.
The vehicle has no DTCs and the MIL is off. Which action is correct?
A. Perform the tailpipe ASM test and certify if it passes.
B. Reject the vehicle because the catalyst monitor is not ready; advise the customer to
complete a drive cycle.
C. Pass the vehicle because only one monitor is incomplete and there are no DTCs.
D. Perform an OBD II functional check only and issue a certificate if no DTCs are
present.
Answer: B. Reject the vehicle because the catalyst monitor is not ready; advise the
customer to complete a drive cycle.
Rationale: California requires all applicable readiness monitors (except EVAP on some
vehicles) to be 'Ready' before an OBD II inspection can be completed. A 'Not Ready'
catalyst monitor indicates insufficient drive time; the vehicle must be driven to complete the
monitor, then re-inspected. Tailpipe testing is not an option when OBD II is the required
test method and monitors are incomplete.
Page 1 of 84
,2. During an ASM test on a 1998 vehicle, HC and CO are within limits, but NOx is 1.5
times the standard. Which component is most likely responsible?
A. Positive crankcase ventilation (PCV) valve
B. Three-way catalytic converter
C. Evaporative emission canister purge valve
D. Air injection reactor (AIR) pump
Answer: B. Three-way catalytic converter
Rationale: High NOx under load typically results from a degraded three-way catalyst's
reduction function or from lean operation/EGR malfunction, but the catalyst is the primary
reduction site for NOx. A failed catalyst can still oxidize HC and CO while failing to reduce
NOx, producing this pattern. PCV, EVAP purge, and AIR pump faults would more likely
affect HC/CO or cause a MIL, not isolated high NOx.
Page 2 of 84
,3. An inspector observes a vehicle with a missing catalytic converter but the OBD II
system shows all monitors 'Ready' and no DTCs. What is the correct disposition?
A. Pass the vehicle because the OBD II system indicates no faults.
B. Fail the vehicle for tampering and issue a citation.
C. Fail the vehicle for a missing required emission control component and refer for
repair.
D. Perform a tailpipe test; if it passes, certify the vehicle.
Answer: C. Fail the vehicle for a missing required emission control component and
refer for repair.
Rationale: Visual inspection for required emission control components is mandatory. A
missing catalytic converter is a tampering violation regardless of OBD II readiness or DTC
status. The inspector must fail the vehicle and advise the customer that the component must
be restored before re-inspection.
4. Which of the following best describes the purpose of the California Smog Check
'Low Pressure Fuel Evaporative Test' (LPFET)?
A. Measure fuel tank pressure to detect leaks in the EVAP system.
B. Verify that the fuel cap holds pressure and does not leak.
C. Check the purge valve operation during a drive cycle.
D. Test the fuel pump's ability to maintain pressure under load.
Answer: A. Measure fuel tank pressure to detect leaks in the EVAP system.
Rationale: LPFET applies a low pressure to the EVAP system and monitors pressure decay
to detect leaks in the fuel tank, hoses, and canister. It is not a fuel cap test (that is a
separate cap integrity check), nor does it test the purge valve or fuel pump.
Page 3 of 84
, 5. A vehicle fails the Smog Check due to a MIL commanded on and DTC P0420. The
customer repairs the vehicle and returns. The MIL is off and no DTCs are stored, but
the catalyst monitor shows 'Not Ready'. What should the inspector do?
A. Certify the vehicle because the MIL is off and no DTCs are present.
B. Perform a tailpipe test to confirm the repair.
C. Reject the vehicle until the catalyst monitor is 'Ready'.
D. Clear the DTCs and immediately re-test.
Answer: C. Reject the vehicle until the catalyst monitor is 'Ready'.
Rationale: Even after repairs, the catalyst monitor must be 'Ready' to complete an OBD II
inspection. A 'Not Ready' monitor means the vehicle has not completed the necessary drive
cycle to verify the repair. The inspector cannot certify until the monitor runs and passes.
6. During a visual inspection, an inspector finds a vehicle with a disconnected vacuum
line to the EGR valve. The EGR valve itself is present. How should this be classified?
A. A minor defect that does not affect the inspection outcome.
B. A tampering violation requiring failure and repair.
C. A functional defect that may be overlooked if the vehicle passes the emissions test.
D. A condition that requires the vehicle to be referred to a Referee.
Answer: B. A tampering violation requiring failure and repair.
Rationale: Disconnecting or disabling an emission control component such as the EGR
valve is considered tampering under California regulations. The vehicle must fail
inspection and the component must be reconnected and functional before re-inspection. It
is not a minor defect and cannot be overlooked even if the vehicle might pass an emissions
test.
Page 4 of 84
Examination with Practice Questions And
Correct Answers (
1. A 2005 model-year vehicle arrives for a biennial Smog Check. The OBD II system
shows readiness monitors: Catalyst 'Not Ready', EVAP 'Ready', O2 Sensor 'Ready'.
The vehicle has no DTCs and the MIL is off. Which action is correct?
A. Perform the tailpipe ASM test and certify if it passes.
B. Reject the vehicle because the catalyst monitor is not ready; advise the customer to
complete a drive cycle.
C. Pass the vehicle because only one monitor is incomplete and there are no DTCs.
D. Perform an OBD II functional check only and issue a certificate if no DTCs are
present.
Answer: B. Reject the vehicle because the catalyst monitor is not ready; advise the
customer to complete a drive cycle.
Rationale: California requires all applicable readiness monitors (except EVAP on some
vehicles) to be 'Ready' before an OBD II inspection can be completed. A 'Not Ready'
catalyst monitor indicates insufficient drive time; the vehicle must be driven to complete the
monitor, then re-inspected. Tailpipe testing is not an option when OBD II is the required
test method and monitors are incomplete.
Page 1 of 84
,2. During an ASM test on a 1998 vehicle, HC and CO are within limits, but NOx is 1.5
times the standard. Which component is most likely responsible?
A. Positive crankcase ventilation (PCV) valve
B. Three-way catalytic converter
C. Evaporative emission canister purge valve
D. Air injection reactor (AIR) pump
Answer: B. Three-way catalytic converter
Rationale: High NOx under load typically results from a degraded three-way catalyst's
reduction function or from lean operation/EGR malfunction, but the catalyst is the primary
reduction site for NOx. A failed catalyst can still oxidize HC and CO while failing to reduce
NOx, producing this pattern. PCV, EVAP purge, and AIR pump faults would more likely
affect HC/CO or cause a MIL, not isolated high NOx.
Page 2 of 84
,3. An inspector observes a vehicle with a missing catalytic converter but the OBD II
system shows all monitors 'Ready' and no DTCs. What is the correct disposition?
A. Pass the vehicle because the OBD II system indicates no faults.
B. Fail the vehicle for tampering and issue a citation.
C. Fail the vehicle for a missing required emission control component and refer for
repair.
D. Perform a tailpipe test; if it passes, certify the vehicle.
Answer: C. Fail the vehicle for a missing required emission control component and
refer for repair.
Rationale: Visual inspection for required emission control components is mandatory. A
missing catalytic converter is a tampering violation regardless of OBD II readiness or DTC
status. The inspector must fail the vehicle and advise the customer that the component must
be restored before re-inspection.
4. Which of the following best describes the purpose of the California Smog Check
'Low Pressure Fuel Evaporative Test' (LPFET)?
A. Measure fuel tank pressure to detect leaks in the EVAP system.
B. Verify that the fuel cap holds pressure and does not leak.
C. Check the purge valve operation during a drive cycle.
D. Test the fuel pump's ability to maintain pressure under load.
Answer: A. Measure fuel tank pressure to detect leaks in the EVAP system.
Rationale: LPFET applies a low pressure to the EVAP system and monitors pressure decay
to detect leaks in the fuel tank, hoses, and canister. It is not a fuel cap test (that is a
separate cap integrity check), nor does it test the purge valve or fuel pump.
Page 3 of 84
, 5. A vehicle fails the Smog Check due to a MIL commanded on and DTC P0420. The
customer repairs the vehicle and returns. The MIL is off and no DTCs are stored, but
the catalyst monitor shows 'Not Ready'. What should the inspector do?
A. Certify the vehicle because the MIL is off and no DTCs are present.
B. Perform a tailpipe test to confirm the repair.
C. Reject the vehicle until the catalyst monitor is 'Ready'.
D. Clear the DTCs and immediately re-test.
Answer: C. Reject the vehicle until the catalyst monitor is 'Ready'.
Rationale: Even after repairs, the catalyst monitor must be 'Ready' to complete an OBD II
inspection. A 'Not Ready' monitor means the vehicle has not completed the necessary drive
cycle to verify the repair. The inspector cannot certify until the monitor runs and passes.
6. During a visual inspection, an inspector finds a vehicle with a disconnected vacuum
line to the EGR valve. The EGR valve itself is present. How should this be classified?
A. A minor defect that does not affect the inspection outcome.
B. A tampering violation requiring failure and repair.
C. A functional defect that may be overlooked if the vehicle passes the emissions test.
D. A condition that requires the vehicle to be referred to a Referee.
Answer: B. A tampering violation requiring failure and repair.
Rationale: Disconnecting or disabling an emission control component such as the EGR
valve is considered tampering under California regulations. The vehicle must fail
inspection and the component must be reconnected and functional before re-inspection. It
is not a minor defect and cannot be overlooked even if the vehicle might pass an emissions
test.
Page 4 of 84
