Accent L4-1.6L (2003)
Oxygen Sensor: Technical Service Bulletins
Engine Controls - Oxygen Sensor Function/Diagnosis
SOURCE: Hyundai Tech Net Times Volume 13 Issue 5 2003
TITLE: Oxygen Sensors
APPLIES TO: 96 - 04 All
SERVICE TIP:
An oxygen sensor measures the amount of oxygen present in the exhaust gas. The oxygen sensor ('element') is coated with a catalyst metal that
produces a small voltage from 0 to 1.00 volt at temperatures in the range of 600°F (315°C) when exposed to oxygen. The "stoichiometric" air-fuel
mixture for optimum fuel economy and emissions occurs at approximately 0.50 V. When the oxygen sensor output signal is above 0.50 V, the air-fuel
mixture is considered rich and when the signal is under 0.50 V it is considered lean.
Hyundai OBD II engine management systems (1996 and later models) include two heated oxygen sensors (heated oxygen sensors allow the vehicle to
go into closed loop in 20 to 30 seconds or less to reduce emissions):
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The "upstream" (front) oxygen sensor is located in the exhaust stream before the catalytic converter. The front sensor provides feedback to the
PCM that is used to identify if the air-fuel mixture supplied to the cylinders is rich or lean. Under normal operating conditions, the front oxygen
sensor signal will fluctuate from 0 to 1.00 V. The front sensor signal should fluctuate, crossing the 0.50 V center about seven times in 5 seconds
with the engine held at a steady 2500 rpm, when the vehicle is at operating temperature.
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The "downstream" (rear) oxygen sensor is located after the catalytic converter in the exhaust stream. The rear sensor provides feedback to the
PCM to 'fine tune' the air-fuel ratio and to monitor catalytic converter efficiency. The rear sensor signal will also fluctuate in the 0 to 1.00V range
but the pattern is less predictable than for the front oxygen sensor because of its position in the exhaust system. Once the catalyst has reached
operating temperature, the rear sensor signal should change very little, if at all. If the rear sensor signal fluctuates at approximately the frequency
of the front sensor, it is an indication that the catalytic converter is not at operating temperature or is malfunctioning.
Oxygen Sensor Diagnosis
A properly operating oxygen sensor may have unusual signal characteristics that are the result of other components. A malfunction of any of the
following components may affect sensor signal characteristics:
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Fuel injector(s)
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Air flow sensor
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Evaporative emission system
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Intake air temperature sensor
