Massachusetts Vehicle Check - Mass08 Management Module ...

Non-Commercial
mixture. The charcoal canister and purge process are commonly known as the Evaporative
Emissions System (EVAP). The newer generations of EVAP systems use one of the
following leak detection strategies: applied metered engine vacuum, Leak Detection Pumps
(LDP) or – the latest method – Natural Vacuum Leak Detection (NVLD), to ensure the
system can purge and/or hold EVAP vapors. EVAP systems that are monitored by the
computer may check the integrity by one or all of the following: purge flow, system sealing or
the system’s ability to hold vapors. This process of flow, seal and hold is checked and
reported to the EVAP Monitor, which is a non-continuous monitor.
EGR
Exhaust Gas Recirculation (EGR) is used to reduce NOx emissions. This function is
accomplished by allowing a metered amount of exhaust gas to be reintroduced into the
combustion process to displace oxygen, which then reduces peak combustion temperatures.
EGR systems include an EGR valve, passages, and possibly even transducers and
solenoids, which tend to clog with carbon residue from the exhaust gases it recirculates.
Additionally, this function must occur at the right times and in the right amounts, or engine
emissions and performance suffer dramatically. Today’s EGR systems use computerized
switching devices for precise control of exhaust gases. Testing of the EGR system’s integrity
is monitored by the EGR monitor, which is a non-continuous monitor. Be aware that not all
manufacturers utilize an EGR valve, but instead may use variable valve timing, or other
methods to achieve NOx reductions.
Massachusetts Vehicle Check
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