Question 1

The preliminary standard developed by CARB and used before OBD-II was called _____________.
A)engine manufacturer's diagnostic (EMD) systems
B)OBD-II (On-Board Diagnostics Second Design)
C)OBDI (On-Board Diagnostics)
D)CAN (controller area network)

Accepted Answer

OBDI (On-Board Diagnostics) was the preliminary standard developed by CARB before the implementation of OBD-II.

Question 2

Two technicians are discussing the purpose of OBD-II compliant systems for automotive diesel engines. Technician A says that an OBD-II compliant system is designed to identify or self-diagnose emission-related faults and report fault codes. Technician B says the OBD-II rules are set up to enable drivers to have emissions problems repaired quickly and easily. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician A is correct because OBD-II systems are indeed designed to identify and diagnose emission-related faults and report them via fault codes. Technician B is also correct because the purpose of OBD-II rules is to facilitate the quick and easy repair of emissions problems by alerting drivers to issues.

Question 3

How many wires will transmit and receive signal data for the CAN engine/powertrain network on the diagnostic datalink connector (DLC) for an OBD-II compliant vehicle?
A)Only 1.
B)Two.
C)Four.
D)Five.

Accepted Answer

The CAN (Controller Area Network) bus system in OBD-II compliant vehicles uses two wires, CAN High and CAN Low, to transmit and receive data.

Question 4

An enhanced OBD-II code will be indicated by which position in the SAE code structure?
A)last digit.
B)last two digits.
C)first two digits.
D)second digit.

Accepted Answer

The answer of An enhanced OBD-II code will be indicated...

Question 5

Technician A says that any DTC will immediately illuminate the MIL in the driver's view the moment one is detected. Technician B says that all OBD-II DTCs will take several trips to confirm that a fault is active before switching on the MIL. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Some DTCs will illuminate the MIL immediately, while others require multiple trips to confirm the fault before the MIL is activated.

Question 6

Technician A says that a pending fault will not have a DTC that can be retrieved by a scanner or electronic service tool. Technician B says a pending fault will never have freeze-frame data associated with it. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Pending faults do have a DTC that can be retrieved by a scanner, and they can have freeze-frame data associated with them.

Question 7

While two technicians are examining the many pairs of wires connected to an OBD-II DLC, Technician A says that all the wires are needed to retrieve fault does from the OBD system. Technician B says that only a pair of CAN wires are necessary to retrieve OBD-II fault codes. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician B is correct because only the CAN (Controller Area Network) wires are necessary to retrieve OBD-II fault codes, as they are used for communication between the vehicle's computer systems.

Question 8

Consider a 2018 OBD-II-compliant and Tier 3-compliant diesel engine. What factor or threshold of excess emissions is typically required to illuminate the MIL when a fault in the diesel particulate filter (DPF) is detected?
A)One and a half times FTP emissions standards.
B)Two times FTP emissions standards.
C)Three times FTP emissions standards.
D)There is no FTP multiplier for Tier 3-compliant diesel engines.

Accepted Answer

For Tier 3-compliant diesel engines, the MIL is typically illuminated when emissions exceed two times the FTP emissions standards.

Question 9

Which OBD-II monitor tracks electrical circuits operating engine components that can fail and cause measurable emissions?
A)functional monitor.
B)continuous monitor.
C)comprehensive component monitor (CCM).
D)threshold monitor.

Accepted Answer

The Comprehensive Component Monitor (CCM) tracks electrical circuits operating engine components that can fail and cause measurable emissions.

Question 10

If a coolant temperature sensor shorted to ground, which emissions system monitor would first detect the fault?
A)cooling system monitor.
B)rationality monitor.
C)comprehensive component monitor (CCM).
D)network communication monitor.

Accepted Answer

The comprehensive component monitor (CCM) is responsible for detecting faults in various sensors and components, including the coolant temperature sensor.

Question 11

Which of the following is a critical enabling condition for a 2018 misfire monitor?
A)The engine must be at idle.
B)The engine cannot have a mechanical defect.
C)The fuel tank must be above ¼ tank.
D)The engine has to operate above idle speed.

Accepted Answer

The answer of Which of the following is a critical...

Question 12

Technician A says that if all the sensors and components of the aftertreatment system are removed, the OBD-II system will not be able to detect faults in the absence of electrical signals. Technician B says that the comprehensive component monitor (CCM) will set emission-related fault codes. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

The comprehensive component monitor (CCM) is designed to detect faults in the aftertreatment system, even if all the sensors and components are removed. The CCM will set emission-related fault codes if it detects any problems with the aftertreatment system.

Question 13

Technician A says that only the fuel system monitor will set DTCs for a misfiring injector. Technician says that the fuel system monitor and misfire monitor will set multiple DTCs. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician B is correct because both the fuel system monitor and the misfire monitor can set DTCs for issues related to a misfiring injector.

Question 14

Before returning a vehicle to the customer after repairing the cause of the MIL being illuminated, the technicians should ______________.
A)erase all codes and road test the vehicle until a readiness code is set
B)rescan the vehicle for codes after road testing the vehicle
C)run the emission monitor associated with the fault
D)check for only active codes after road testing the vehicle

Accepted Answer

Erasing all codes and road testing the vehicle until a readiness code is set ensures that the repair has resolved the issue and that the vehicle is operating properly.

Question 15

Which emissions system monitor will detect incorrect injection timing?
A)Injection timing monitor.
B)Comprehensive component monitor (CCM).
C)Rationality monitor.
D)Fuel system monitor.

Accepted Answer

The answer of Which emissions system monitor will detect incorrect...

Question 16

Which of the following changes will take place when a manufacturer updates a software calibration and a technician uploads or flashes the vehicle with the new calibration?
A)All monitors will be set to ready.
B)The calibration identification number will change.
C)The calibration identification (CAL ID) and calibration verification numbers (CVNs) will both change.
D)The CAL ID number will change and CVNs will remain the same.

Accepted Answer

When a new software calibration is uploaded, both the CAL ID and CVNs typically change to reflect the new software version and ensure the integrity of the update.

Question 17

Technician A says that some emission-related DTCs will cause engine power derate to encourage a driver to have the emissions system repaired. Technician B says that most diesel engine OBD DTCs will derate engine power. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician A is correct because certain emission-related Diagnostic Trouble Codes (DTCs) can trigger a power derate to prompt the driver to address the emissions issue. However, not all diesel engine OBD DTCs will result in a power derate, so Technician B is incorrect.

Question 18

Technician A says that the OBD system on a diesel is continuously judging all major emissions systems for faults. Technician B says that some emissions monitors do not run every drive cycle and take time to correctly judge emissions system operation. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician B is correct because some emissions monitors in the OBD system do not run every drive cycle and require specific conditions to be met before they can accurately assess the emissions system's operation.

Question 19

While two technicians are discussing what to do to prepare a vehicle to pass an OBD-II emissions system inspection with an noncontinuous monitor DTC that causes the MIL to illuminate, Technician A says that the problem would need to be repaired and that the monitors all need to successfully run to pass. Technician B says that just the code could be erased before sending the customer to the inspection. The fault could be fixed after the vehicle has passed the OBD-II inspection test. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

The problem would need to be repaired and that the monitors all need to successfully run to pass.

Question 20

Technician A says that anytime the tailpipe NOx sensor reads more than a few parts per million of NOx, DTCs will switch the MIL on. Technician B says that model predictive control (MPC) will always make adjustments to the engine to correct the fault. Who is correct?
A)Technician A
B)Technician B
C)Both A and B
D)Neither A nor B

Accepted Answer

Technician A is incorrect because the MIL (Malfunction Indicator Lamp) is not triggered by just a few parts per million of NOx; it requires a significant fault. Technician B is incorrect because model predictive control (MPC) does not always make adjustments to correct faults; it predicts and optimizes performance but may not address all faults directly.

Quiz 19: On Board Diagnostics

The preliminary standard developed by CARB and used before OBD-II was called _____________.

How many wires will transmit and receive signal data for the CAN engine/powertrain network on the diagnostic datalink connector (DLC) for an OBD-II compliant vehicle?

An enhanced OBD-II code will be indicated by which position in the SAE code structure?

Technician A says that any DTC will immediately illuminate the MIL in the driver's view the moment one is detected. Technician B says that all OBD-II DTCs will take several trips to confirm that a fault is active before switching on the MIL. Who is correct?

Technician A says that a pending fault will not have a DTC that can be retrieved by a scanner or electronic service tool. Technician B says a pending fault will never have freeze-frame data associated with it. Who is correct?

While two technicians are examining the many pairs of wires connected to an OBD-II DLC, Technician A says that all the wires are needed to retrieve fault does from the OBD system. Technician B says that only a pair of CAN wires are necessary to retrieve OBD-II fault codes. Who is correct?

Consider a 2018 OBD-II-compliant and Tier 3-compliant diesel engine. What factor or threshold of excess emissions is typically required to illuminate the MIL when a fault in the diesel particulate filter (DPF) is detected?

Which OBD-II monitor tracks electrical circuits operating engine components that can fail and cause measurable emissions?

If a coolant temperature sensor shorted to ground, which emissions system monitor would first detect the fault?

Which of the following is a critical enabling condition for a 2018 misfire monitor?

Technician A says that only the fuel system monitor will set DTCs for a misfiring injector. Technician says that the fuel system monitor and misfire monitor will set multiple DTCs. Who is correct?

Before returning a vehicle to the customer after repairing the cause of the MIL being illuminated, the technicians should ______________.

Which emissions system monitor will detect incorrect injection timing?

Which of the following changes will take place when a manufacturer updates a software calibration and a technician uploads or flashes the vehicle with the new calibration?

Technician A says that some emission-related DTCs will cause engine power derate to encourage a driver to have the emissions system repaired. Technician B says that most diesel engine OBD DTCs will derate engine power. Who is correct?

Technician A says that the OBD system on a diesel is continuously judging all major emissions systems for faults. Technician B says that some emissions monitors do not run every drive cycle and take time to correctly judge emissions system operation. Who is correct?

Technician A says that anytime the tailpipe NOx sensor reads more than a few parts per million of NOx, DTCs will switch the MIL on. Technician B says that model predictive control (MPC) will always make adjustments to the engine to correct the fault. Who is correct?