User guide

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EVAP or Evaporative Emissions System
This system works to prevent the escape of fuel vapors into the
atmosphere. The system works by drawing fumes from the fuel
tank into the engine for combustion. Several components can make
up this system, including charcoal canisters, a purge soleniod, fuel
cap, and connecting tubes.
Evaporative System Monitor
This non-continuous monitor checks the EVAP system. The EVAP
monitor checks the proper fuel vapor flow to the engine and pres-
surizes the system to check for leaks. If you have an EVAP fault, or
the system has failed its test, the gas cap should be the first place
you check. This is a "Two-Trip" monitor. See also EVAP.
EGR or Exhaust Gas Recirculation Valve
The EGR valve recirculates small amounts of exhaust gas back into
the intake manifold, where it is mixed with the incoming air/fuel
mixture. This process reduces combustion temperatures by up to
500°F. By reducing the temperature in the combustion chamber,
NOx emissions can be reduced.
Exhaust Gas Recirculation (EGR) Valve Monitor
This non-continuous monitor checks the EGR valve for low and
high flow rates among other parameters. The components of the
EGR Valve Monitor are EGR Valve, EGR soleniod, EGR backpres-
sure transducer, and connecting hoses. This is a "Two-Trip" moni-
tor. See also EGR.
Freeze Frame
A snapshot of the vehicle’s sensor data when the engine computer
determined that a fault has occurred. Freeze frame gives the data as
to what the engine was doing when the DTC responsible for the
freeze frame was triggered. This extra insight can help determine
what conditions contributed in creating the fault.
Fuel System Monitor
A continuously run monitor that checks the short- and long-term
fuel trim. Should either fuel trim stay in or reach their limits for too
long, a stored DTC will record and the MIL will illuminate. The