O2 Monitor Test
OBD II regulations require applicable vehicles monitor and test oxygen
(O2) sensors to determine problems related to fuel and emissions. The
O2 Monitor Test allows retrieval of completed O2 sensors monitor
9The O2 Monitor Test is not an on-demand test. O2 sensors
are not tested when selected via the menu. O2 sensors are
9If the vehicle communicates using a controller area network
(CAN), O2 Monitor tests are not supported by the vehicle. A
message is displayed. See Diagnostic Monitor Test to see
O2 monitor data.
O2 sensors are located before (upstream) and after (downstream)
catalyst(s). Sensors are named (xy) for their position to both cylinder
banks and catalysts.
1y while O2
The O2 sensor upstream of catalyst (closest to engine) has
x2. If vehicle contains more catalysts, O2 sensor downstream
3 and O2 sensor downstream
For example, O2S21 is upstream O2 sensor for cylinder bank
Diagnostic Monitor Test
The Diagnostic Monitor Test function is useful after servicing or after
erasing a vehicle’s memory. Test results do not necessarily indicate a
faulty component or system.
Non-CAN vehicles Diagnostic Monitor Test receives test results for
emission-related powertrain components and systems that are not
CAN vehicles Diagnostic Monitor Test receives test results for
emission-related powertrain components and systems that are and
are not continuously monitored.