Chrysler 2005 Crossfire SRT6 Service Manual page 2992

14 - 54 FUEL INJECTION ZH
O2 SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and protrude into the vehicle exhaust system. The vehicle uses a total
of 4 sensors; 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). The right
upstream sensor (1/1) is located in the right exhaust pipe just before the mini-catalytic converter. The left upstream
sensor (2/1) is located in the left exhaust pipe just before the mini-catalytic converter. The right downstream sensor
(1/2) is located in the right exhaust downpipe just after the mini-catalytic converter, and before the main catalytic
converter. The left downstream sensor (2/2) is located in the left exhaust downpipe just after the mini-catalytic con-
verter, and before the main catalytic converter.
OPERATION
An O2 Sensor is a galvanic battery that provides the Powertrain Control Module (PCM) with a voltage signal (0–1
Volt) inversely proportional to the amount of oxygen in the exhaust. In other words if the oxygen content is low, the
voltage output is high; if the oxygen content is high, the voltage output is low. The PCM uses this information to
adjust injector pulse-width to achieve the 14.7 to 1 air/fuel ratio necessary for proper engine operation and to control
emissions. The O2 Sensor must have a source of oxygen outside the exhaust stream for comparison. Current O2
Sensors receive their fresh oxygen (outside air) supply through the O2 Sensor case housing. Four wires (circuits)
are used on each O2 Sensor: a 12–Volt feed circuit for the sensor heating element, a ground circuit for the heater
element, a low-noise sensor return circuit to the PCM and an input circuit from the sensor back to the PCM to
detect sensor operation.
As vehicles accumulate mileage, the catalytic convertor deteriorates. The deterioration results in a less efficient cat-
alyst. To monitor catalytic convertor deterioration, the fuel injection system uses two heated oxygen sensors. One
sensor upstream of the catalytic convertor, one downstream of the convertor. The PCM compares the reading from
the sensors to calculate the catalytic convertor oxygen storage capacity and converter efficiency. Also, the PCM
uses the upstream heated oxygen sensor input when adjusting injector pulse width.
When the catalytic converter efficiency drops below emission standards, the PCM stores a Diagnostic Trouble Code
(DTC) and illuminates the Malfunction Indicator Lamp (MIL).