Neon L4-2.0L SOHC (1995)
the upstream oxygen sensor tells the PCM how well its output signal is controlling the air/fuel ratio. Variations in the signals from the O2 sensor
serve as air/fuel ratio indicators. Changes in the sensor signal occur because the air/fuel ratio is constantly changing. When oxygen content is low
(rich mixture), the voltage signal will be approximately 1 volt. When oxygen content is high (lean mixture), the voltage signal will be low,
approximately 0.1 volt. The heater element helps the O2 sensor quickly reach a normal and steady operating temperature, which is required for
proper emission control.
POSSIBLE CAUSES:
-
Open heater element circuit
-
O2 sensor failure
Upstream O2 Sensor Shorted to Ground
NAME OF CODE:
Upstream O2 Sensor Voltage Shorted to Ground
WHEN MONITORED:
With the ignition key off, after the engine cools down.
SET CONDITION:
The upstream oxygen sensor signal voltage is below 0.156 volts prior to O2 sensor heater test.
THEORY OF OPERATION:
The upstream oxygen sensor is a voltage generating device. The PCM receives exhaust gas information from this O2 sensor. The sensor detects
exhaust gas content by a galvanic reaction within the sensor that produces a voltage. After measuring the amount of oxygen in the exhaust gases,
the upstream oxygen sensor tells the PCM how well its output signals are controlling the air/fuel ratio. Variations in the signal from this O2 sensor
serve as air/fuel ratio indicators. Changes in the sensor signal occur because the air/fuel ratio is constantly changing. When oxygen content is low
(rich mixture), the voltage signal will be approximately 1 volt. When oxygen content is high (lean mixture), the voltage signal will be low,
approximately 0.1 volt.
POSSIBLE CAUSES:
-
Sensor output wire shorted to another circuit
-
Dirty/wet connection causing voltage tracking in connector
-
O2 sensor failure
-
PCM failure
-
Connector terminals
-
Connector wires
Upstream O2 Sensor Shorted to Voltage
NAME OF CODE:
Upstream O2S Shorted To Voltage
WHEN MONITORED:
With the ignition key ON.
SET CONDITION:
The upstream oxygen sensor signal voltage is above 1.2 volts.
THEORY OF OPERATION:
The upstream oxygen sensor is a voltage generating device. The Powertrain Control Module (PCM) receives exhaust gas information from this O2
sensor. The sensor detects exhaust gas content by a galvanic reaction within the sensor that produces a voltage. After measuring the amount of
oxygen in the exhaust gases, the upstream oxygen sensor tells the PCM well its output signals are controlling the air/fuel ratio. Variations in the
signal from this O2 sensor serve as air/fuel ratio indicators. Changes in the sensor signal occur because the air/fuel ratio is constantly changing.
When oxygen content is low (rich mixture), the voltage signal will be approximately 1 volt. When oxygen content is high (lean mixture), the
voltage signal will be low, approximately 0.1 volt.
POSSIBLE CAUSES:
-
Sensor output wire shorted to another circuit
-
Dirty/wet connection causing voltage tracking in connector
-
O2 sensor failure
Upstream O2 Sensor Slow Response
NAME OF CODE:
Upstream O2S Response
WHEN MONITORED:
With the engine running for more than 3 minutes, engine temperature greater than 170° F, after reaching a vehicle speed of 24 MPH, at idle with
