Just below firewall on exhaust pipe.
Before the Cat Conv
How_do_you_reset_a_1990_Cadillac_DeVille_computer_system_after_self-servicing
To replace the O2 sensor on a 1997 Cadillac Seville STS, first, ensure the vehicle is cool and disconnect the negative battery cable. Locate the O2 sensor, which is typically found on the exhaust manifold or downstream in the exhaust system. Use a wrench or O2 sensor socket to unscrew the old sensor, then install the new one, ensuring it’s tightened securely. Finally, reconnect the battery and check for any error codes or leaks.
I believe the O2 sensor heater is a fused circuit, you will need a wiring diagram to tell which one it is.
its part of the exhaust system
It is located about in center of the engine compartment on the backside of the motor against the firewall...right above the exhaust manifold. That would be the upstream o2 sensor. The downstream o2 sensor is located somewhere on the exhaust just after the exhaust manifold...
It is located in the exhaust manifold.
on the rear exhaust manifold, directly behind the motor
Heated Oxygen Sensor Control Circuit (Bank 1 Sensor 2)symptomsOther 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 sensorReplace PCM if circuit has failed and no wiring issues present, good O2 sensor
It's located under the car on the exhaust pipe,probably has carbon build up on it. You can buy an o2 sensor tool from auto parts store
Near the starter on the exhaust header. If it is 1990 it will be fun to break the rusty sensor out of the truck. good luck
Oxygen sensor circuit open. Check if the wire is plugged in or broken. If it is then replace the O2 sensor.