Cadillac DeVillethese o2 sensors are located aft of the cat that is o2 #2 ,o2 #1 is forward of the cat this is the same on all OBDII compliant auto's Fred@email@example.com
The O2 sensor on a 2003 Cadillac Northstar engine is located in the exhaust manifold. The readings from this sensor are sent to the vehicle's computer, which makes constant adjustments to the fuel and air mixture.
That would be the O2 sensor after the catalytic converter.
The bank 1, sensor 3, O2 sensor would be the O2 sensor post cat.
It is the O2 sensor screwed into the front of the catalytic converter
The upstream O2 sensor is mounted in the ehxaust manifold The downstream O2 sensor is mounted in the exhaust pipe after the catalytic converter
I believe the O2 sensor heater is a fused circuit, you will need a wiring diagram to tell which one it is.
Before the Cat Conv
Heated Oxygen Sensor Control Circuit Bank1 Sensor2symptomsOther than the MIL light illuminating you may not notice any performance issues.causeA short in the O2 sensor heater circuit or the sensor itselfA faulty O2 sensor heaterWiring or connectors are broken or frayed to the sensor or relayBad PCM or ECMThe fixCorrect wiring short or loose connector found in inspection.and/orReplace the bank 1 sensor 2, O2 sensor
The O2 sensor can be found on the exhaust manifold or just after and behind the catalitic convertor
o2 sensor is on driver side 2nd one back