Download SOLUTIONS

EXAMPLE
PATTERN
The voltage is generated by a sensor that has a probe assembly which contacts the exhaust stream. This probe assembly is made up of a compound called zirconium dioxide,
which is an electrically conductive material that can generate small voltages when in
contact with oxygen. The probe tip is also coated with platinum to aid in this process.
The downstream, or after converter, oxygen sensors measure the amount of oxygen
present in the exhaust after the converter. Generally, the wave form of a system with a
properly operating catalyst will show little or no voltage fluctuation on an oscilloscope.
EXAMPLE
PATTERN
The catalytic converter is comprised of an internal substrate onto which a chemical
washcoat is placed. It extends the geometric surface area of the substrate and also acts
as an absorbing or storing material for oxygen in the exhaust. On to this substrate the
precious metals are impregnated that cause the catalytic reactions with the pollutants.
Ceramic Monotlith
Substrate shown
When the engine burns a lean air/fuel mixture, high amounts of oxygen from the exhaust
stream flow through the substrate of the catalytic converter. The washcoat on the substrate absorbs this excess O2 and stores it for use during rich air/fuel mixtures when it is
released to help in the oxidation process.
A proper functioning catalytic converters downstream, or after converter oxygen sensor, will show little or no fluctuation in voltage. If catalytic converter degredation occurs
affecting the oxygen storage capacity of the washcoat, a fluctuating voltage signal will
be sent to the vehicles computer which will in turn illuminate the (MIL) Malfunction Illumination Light. This will notify the driver of a problem. The vehicles computer has an
algorithm stored in it which allows the computer to determine converter efficiency by the
amount of oxygen obsorbed. The catalyst monitor is a Non Continuous Monitor. This
type runs one time per drive trip.
THE FUEL SYSTEM MONITOR
The fuel system monitor controls fuel trim to the engine. The vehicles computer allows
for fine tuning of the air/fuel ratio. The computer actually stores information on fuel
trim and compares this to a pre-programmed based fuel calculation. Fuel trim can be
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