Week 1, Chapter 64 - OBD Flashcards
What light is illuminated when a vehicle has identified a fault that is likely causing it not to comply with clean air regulations?
Check Engine Light
The ____ runs the engine management systems through self-tests at engine start-up and continues to monitor the systems once underway
PCM
What kind of computers monitor systems and components and inform vehicle operator when a fault occurs?
Onboard Diagnostic (OBD) Systems
Which OBD generation includes these…
- Became nationwide in 1981
- Allowed each vehicle manufacturer to have its own OBD system
- No set standards for DTC’s
- Basic information from a scan tool
- Flash diagnostics
OBD I
Which OBD generation includes these…
- Operate under standards set by SAE
- Standardized nationwide in 1996
- Constantly monitor and manage the engine management system
OBD II
- Sensor data can be accessed with a scan tool
- Scan tool can be used to access the information from any sensor in the system
- All of the sensor data can be examined while diagnosing faults
These this are all included in what?
Data Stream, or Parameter Identification (PID)
A ____________ is a localized vehicle network that enables computers and components to send and receive signals across a shielded twisted pair of wires
CANbus
What kind of wires are shielded by being twisted around one another and carry balanced signals between modules?
Twisted Pair Wires
An ignition cycle in which the key is turned on, a monitor runs, the key is turned off and the PCM powers down
Trip
A trip when the engine is started and run until the engine operating temperature reaches 160°F and has increased in temperature at least 40°F and the engine is turned off again
Warm-up Cycle
When all monitors have run and passed (this may take a very long time)
Drive Cycle
Conditions that must be met for a monitor to run such as certain temperatures, speed, what the sensor is being used for at the time, etc.
Enabling Criteria
The conditions that were occurring when a monitor failed
Similar Conditions Window
A snapshot of parameters taken on the first failure of a monitor
Freeze Frame Data
Live data or freeze frame data that provides sensor and actuator information to the technician
Parameter Identification (PID)
_____________________ is a list of sensor data that are associated with a specific DTC and is listed in order of highest priority to lowest priority DTC’s
Freeze Frame Data
___________ indicate the component or circuit in which a fault has been detected and are stored in one or more of the vehicle’s electronic control modules
Diagnostic Trouble Codes (DTCs)
Once the MIL is on, it will remain on until either the technician clears the codes, or the fault has not been detected during ____ consecutive trips when the monitor is run without failure
3
Pending/current codes that have happened in the past, but haven’t been cleared manually with a scan tool, and will stay for up to 80 warm up cycles depending on the severity of the fault
History Codes
_________ DTC’s are priority. These set the check engine light on the first failure of a monitor, and if the problem is severe enough, the check engine light will flash in order to alert the driver that there is something causing damage to the emission control systems of the vehicle.
Type A
_________ DTC’s are generally a two-trip fault in which freeze frame data is set on the first failure of a monitor and on the second failure, the MIL is illuminated
Type B
________ DTC’s are non-priority for emissions. These include:
- ABS, TCS, Restraints, Oil change reminders, maintenance reminders, etc.
Type C
Position 1 of a DTC determines the…
Major System at fault
Position 2 of a DTC determines the…
Determination
Position 3 of a DTC determines the…
System that is failing
Position 4/5 of a DTC is the…
Serial numbering of the individual components or systems
- Misfire monitor
- Fuel System monitor
- Continuous component monitor
These are examples of…
High priority faults
- Catalytic converter monitor
- Heated catalyst monitor
- Oxygen sensor monitor
- Oxygen sensor heater monitor
- Evaporative system monitor
- EGR system monitor
- Secondary air system monitor
These are all examples of…
Lower priority faults
________________ monitors are run only once during each engine warm-up cycle, or even less often
Non-continuous
A _________ is defined as a lack of combustion
Misfire
The PCM uses the __________________ to tell which cylinder(s) are misfiring or if it is a random misfire
Camshaft Position Sensor (CMP)
If the monitor detects misfires between the lower and upper threshold, a “______________” will be set, and freeze-frame data may be stored
Pending DTC
_________ monitors the amount of correction needed to keep the air-fuel mixture correct
Fuel System Monitor (Continuous)
Base fuel trip is considered __% as a scan tool value
0%
_____________ fuel trim numbers indicate the PCM is adding fuel compared to the base fuel trim. This indicates a lean condition.
Positive
__________ fuel trim numbers indicate the PCM is taking away fuel compared to the base fuel trim. This indicates a rich condition
Negative
The largest overall monitor is the _____
Comprehensive Components Monitor (CCM)
A CCM checks inputs for ___________
Rationality
A CCM checks outputs for ______________
Functionality
What component monitors and controls exhaust emissions?
Oxygen Sensor Monitor
What is it called when the engine PCM uses the oxygen sensor signal for correction of the A/F ratio
Closed Loop Operation
What is it called when the engine ECU does not use the oxygen sensor signal for correction of the A/F ratio
Open Loop Operation
A properly operating ___________________ must:
- generate a signal below a specified low voltage and above a specified high voltage
- change voltage quickly
Oxygen Sensor
What does the OBD II monitor also measure during a short time period?
The rich-lean switching frequency of the oxygen sensor output
Doing what to the oxygen sensors can get them into operation much sooner?
Heating them up
If the time for the oxygen sensor to operate is too long on two consecutive drive cycles, what happens?
A DTC is set
What component reduces pollutants in the exhaust system?
Catalytic Converter Monitor
To run the ________, the engine must typically be below a specified temperature, and the fuel level must be between 1/4 and 3/4 full
EVAP Monitor
The EVAP monitor draws a vacuum on the EVAP system, seals it off, and then monitors the pressure to determine what?
If there are any leaks
What component monitors the flow of Exhaust Gas Recirculation gases when the valve is commanded open?
EGR System Monitor
EGR system monitor is run after the engine is fully ________ and has met other specified conditions based on the type of monitoring sensor used
Warmed up
What are the most common EGR monitoring sensors used to determine operation?
- EGR temperature sensor method
- MAP sensor method
- Oxygen sensor method
What is able to electronically communicate with and extract data from the vehicle’s one or more onboard computers?
Scan Tools
What kind of scanners are used to send commands to the
Bidirectional Scanners
