Definitions of Terminology

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Defintions of Terminology

A/F Ratio Air Fuel Ratio.
A/F Ratio Sensor A four wire, heated oxygen sensor that more precisely measures A/F ratio than do traditional sensors.
Aftermarket Sensor A sensor made to replace OE sensors.
PCM Powertrain Control Module
ECM Electronic Control Module
CEL Check Engine Light.
Closed Loop Mode When the oxygen sensor(s) are operational in a vehicle’s diagnostics
DTC Diagnostic Trouble Code
Direct Fit Sensor A sensor with a connector that fits an existing connector directly.
DIY Installer Do It Yourself. An individual that works on his or her own vehicle.
Downstream The sensor position after the catalytic converter. Also known as post-cat.
ECU Engine Control Unit
FLO Sensor Fast Light Off Sensor. This design can reach operating temperature in as little as 10 seconds.
Heated Sensor An oxygen sensor design that utilizes an internal heater.
Lean A condition where there is an excess of oxygen in the exhaust stream
MIL Malfunction Indicator Lamp
OBDII The current onboard diagnostic language used by passenger vehicles.
OE Sensor A sensor that is installed on a factory vehicle
Open Loop Mode When the oxygen sensor(s) are not engaged in a vehicle’s diagnostics
Planar Sensor A sensor made of layers of zirconia & alumina bonded together, allowing for faster warm up of the sensor
Rich A condition where there is a shortage of oxygen in the exhaust stream
Stoichiometric The ideal air fuel ratio of 14.7:1 air: fuel by mass for gasoline engines
Titania Sensor A sensor design that employs the use of titanium instead of zirconia
UFLO Sensor Ultra Fast Light Off Sensor. The oxygen sensor design that will reach operating temperature in the least amount of time possible.
Universal Sensor A sensor with no connector that must be installed through splices
Unheated Sensor An early, basic sensor design that relies on external heat
Upstream The sensor position before the catalytic converter. Also known as pre-cat
Wideband A five wire, heated oxygen sensor that utilizes patented technology to provide a better measurement of A/F ratio than do four wire sensors
Zirconia A white, crystalline compound that is used in oxygen sensors
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