Neon L4-2.0L SOHC (1995)
Oxygen Sensor: Description and Operation
Related Trouble Codes & Set Conditions
Downstream O2 Sensor Heater Failure
NAME OF CODE:
Downstream O2S Heater Failure
WHEN MONITORED:
With the ignition key OFF, after the engine cools down.
SET CONDITION:
No sensor output signal is received when the PCM powers up the sensor heater.
THEORY OF OPERATION:
The downstream 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 downstream oxygen sensor tells the PCM how well the catalytic converter is oxidizing HC and CO components and reducing NOx components
in the engine exhaust gas. This O2 sensor serves as an indicator of oxygen content. 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
Downstream O2 Sensor Shorted to Ground
NAME OF CODE:
Downstream O2S Shorted To Ground
WHEN MONITORED:
With the ignition key OFF, after the engine cools down.
SET CONDITION:
The downstream oxygen sensor signal voltage is below 0.156 volts prior to O2 sensor heater test.
THEORY OF OPERATION:
The downstream 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 downstream oxygen sensor tells the Powertrain Control Module (PCM) how well the catalytic converter is oxidizing HC and CO components
and reducing NOx components in the engine exhaust gas. Variations in the signals from this O2 sensor serve as an indicator of oxygen content.
The catalytic converter absorbs the oxygen in the exhaust gas when the fuel/air mixture is lean. The downstream O2 sensor indicates a deficiency
of oxygen when the upstream O2 sensor detects an abundance of oxygen and vice versa.
POSSIBLE CAUSES:
-
Sensor output wire shorted to another circuit
-
Dirty/wet connection causing voltage tracking in connector
-
O2 sensor failure
-
PCM failure
-
Connector terminals/wires
Downstream O2 Sensor Shorted to Voltage
NAME OF CODE:
Downstream O2S Shorted To Voltage
WHEN MONITORED:
With the ignition key ON.
SET CONDITION:
The downstream oxygen sensor signal voltage is above 1.2 volts.
THEORY OF OPERATION:
The downstream 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 downstream oxygen sensor tells the Powertrain Control Module (PCM) how well the catalytic converter is oxidizing HC and CO components
