Emissions Readiness - UltraGauge EM plus Installation & Operation Manual

Emissions Readiness

The Vehicle's Engine Control Module (ECM) performs two types of tests on the vehicle's emission system. The first type is a continual
test or real-time test in which the ECM continually monitors the state of various system sensors to determine if the system is operating
normally or if the system is outside of design specifications. For example, during normal operation should the coolant temperature
suddenly output the lowest or highest possible value, the system assumes a temperature sensor fault has occurred. Typically the ECM
then lights the "Check Engine Light" and posts a trouble code.
The second type of test is a non-continuous test and often referred to as a "monitor". This type of test is a long term test carried out
during a "driving cycle". Where the "driving cycle" might constitute the following:
Example driving cycle
1. A cold start
2. A certain amount of idle time
3. A certain level of acceleration (say 50%)
4. Maintain a highway speed for a given time (55MPH for 3 minutes)
5. Deceleration for a given time
6. A higher level of acceleration (say 80%)
7. Again hold a steady speed
8. Decelerate
The above is just an example, and each manufacturer will likely have a different "driving cycle". Normally, the ECM will check off each
of the driving cycle stages as they happen and they may or may not be in a particular order. Ultimately it's best to search the web to
determine if the driving cycle for your vehicle is known.
During the "driving cycle" several readiness tests may be performed. The tests performed are manufacturer dependent.
Readiness
Test/Monitor
Catalyst Monitors the condition of the Catalytic Converters. Condition is determined by monitoring the O2 sensors before
and after the catalytic converters
Heated Catalyst Catalytic converters work best when hot. To quicken the effectiveness of the converters, most late model vehicles
electrically heat the catalytic converters. This test monitors the condition of the electrical heaters.
Evaporative Monitors the Evaporative System which is present to collect fuel vapor and later feed such vapors into the engine.
System
Secondary Air Some vehicles have a secondary air system which injects additional air (oxygen) into the exhaust system in an
System attempt to further burn any unconsumed fuel. This monitor checks the condition of the various switches, solenoids,
valves, etc. that make up the secondary air system
Oxygen Sensor Monitors the operation of the vehicle's Oxygen sensors. O2 sensors measure the amount of Oxygen in the exhaust
system and allow the ECM to properly set the air-fuel mixture.
Oxygen Sensor Oxygen sensors do not function until they are hot. Most modern vehicles use an electrical heating element
heater integrated into the O2 sensor to rapidly heat the sensor when the vehicle is cold. This monitor ensures the operation
of the heating element in the O2 sensor.
EGR and/or The Exhaust Gas Recirculator system allows exhaust gases to re-enter the combustion chamber. Counter
Variable Valve intuitively, this gas reduces the combustion chamber temperatures and reduces Nitric Oxide emissions. This
Timing monitor ensures that the components of the system are operating correctly. The function of the EGR valve can also
be accomplished with variable valve timing. With this approach there is a very small window where both the intake
and exhaust valves are open (if only slightly), and the exhaust can re- enter the cylinder during the intake stroke.
Fuel System The ECM monitors the air fuel ratio by monitoring the O2 sensors to determine if the fuel system is operating
properly. This is a continuous real-time test. The OBDII standard requires that the ECM always report the status
as ready. As such there is no point reporting the Fuel System monitor status, and it is not supported by UltraGauge
Misfire Engine cylinder misfires test. When the engine misfires, with all else being constant, there is a measurable decrease
in RPMs. Combined with the CAM shaft position sensor, the offending cylinder can be identified. For gasoline
engines, this is a continuous/real-time test and the Misfire monitor status always reads ready. Hence, the status is
not displayed by UltraGauge. Misfire readiness is provided for Diesel engines.
AC System The air conditioning system monitor was proposed when the alleged Ozone depleting R12 refrigerant was common.
The Federally mandated replacement of R12 with R134a occurred in 1994. The OBDII was standardized two years
later in 1996. Since R12 was replaced, the AC system monitor was no longer needed and was never made part of
the OBDII standard. However, some manufacturers may have preemptively included the monitor into their ECMs
in anticipation of the OBDII standard. In such an event, the monitor may be in place, but the vehicle will have
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Description (Gasoline Engines)
UltraGauge™ EM User Manual www.ultra-gauge.com