Its right on the exhaust manifold, if u look down from the top u should see the cable and be able to locate it.
There is also a rear O2 sensor between the header and the catalytic converter.
Depending on if you have a Cali Spec eclipse or a Fed. Spec eclipse, If you have a Federal Spec. you only have an oxygen sensor before the cat and right after the cat. and you won't have one in the header.
The upstream heated oxygen sensor is located ahead of the catalytic converter The downstream heated oxygen sensor is located behind the converter
You can find them in the exhaust pipe. Depending on engine size you might have anywhere from 2 to 4 oxygen sensors.
follow the exhaust vent from the engine, if it's anything like my 97 eclipse it should be a few feet from the bumper on the underside, not convenient but you should be able to reach it without blocks or a lift.
The 1988 Toyota oxygen sensor is located on the air cleaner housing. You will find the sensor, on the back side of the housing.
Find cylinder one, usually on the driver side. That is Bank one side, then go to the second O2 sensor, which will be the one after the cat converter.
You can find it in the exhaust manifold. There is only one sensor over there. Sometimes the sensor is called oxygen sensor because on some Camry models at the same location the oxygen sensor is installed. Most of camries have oxygen sensor.
You can find the starter relay switch in your 2000 Mitsubishi Eclipse in the fuse box. The starter relay switch will be in the third column, at the top.
Upstream Oxygen Sensor heater performance. That will be the first oxygen sensor in the exhaust pipe ( closest to the engine ) on the passenger side head. You need to check the wireing connector that hooks to the oxygen sensor for a broken wire are bad connection. If you find no problems, then replace oxygen sensor.
You can find it in the cylinder head next to the oxygen sensor harness.
P0125 is about coolent temp. sensor the problem is not the coolent sensor. When you have lazy Oxygen sensor you get this code. It is sensor 1 but you need to find out which bank, the only way you can find this out by snapon scanner.
The 1991 Pontiac Grand Prix oxygen sensor is located on the outside of the air filter housing. You will find the sensor on the back side of the air filter housing.