Specify your engine size, or were they all the same? BClear.
If the Trooper has the 3.5L v6, there are 4 SO2 sensors. There are two banks right and left, or bank 1 and bank 2 respectively. Then there is a sensor upstream from the catalytic converter on each bank (sensor 1) , and one down stream (sensor 2).Hope this helps/
The exhaust system has two banks. Each bank has two oxygen sensors. Bank one is on the driver's side. Oxygen sensor 1 is between the exhaust manifold and the catalytic converter. Oxygen sensor 2 is behind the converter.
According to my Chilton repair manual : " the oxygen sensor is used with the feedback system to sense the presence of oxygen in the exhaust gas and signal the computer which can reference the voltage signal to an air / fuel ratio " ( that applies to bank 1 - passenger side , and bank 2 - drivers side , sensor 1 ) banks 1 + 2 , sensor 2 is downstream of the catalytic converters and are called catalyst monitors
Bank 2 is the bank (you have a V6 engine with two banks of three cylinders) with cylinder #6. This is the left hand side of the engine. If you stand there facing the belts and but your two hands out, your right hand will be near bank two and your left hand will be near bank 1. Follow the exhaust system from the engine back toward the tailpipe. The second oxygen sensor you encounter is bank 2 sensor 2. Unplug the sensor. Use an oxygen sensor wrench or oxygen sensor socket to unscrew the sensor. If the sensor won't unscrew easily, start the engine and rev it up to abour 2500 RPM for about 3 minutes, then try unscrewing the sensor with the engine still running. Don't burn yourself. If your tool won't fit well, use a 6-point 7/8 inch box wrench. You can cut the sensor lead if necessary as you've already determined that the old sensor is no longer useful. Screw the new sensor in, then plug it in. Reset PCM codes.
Open the hood, look down at the exhaust manifold and find the device that looks a little like a sparkplug; it should be screwed into the exhaust manifold near the junction... that's the oxygen sensor.Trace back the wire to a plug and disconnect it.Unscrew the oxygen sensor. It's usually easiest if you have the specially designed socket, but it's not absolutely necessary.SAVE THE WIRE!!! Most replacement oxygen sensors will require that you splice the wires from the sensor onto the wires of the original plug assembly.AFTER you've spliced the wires, put the new oxygen sensor in place.Now do the same to the OTHER side... the L300 has a V6 engine. A V6 uses 2 exhaust banks and 2 oxygen sensors. You'll save yourself a boatload of trouble if you replace them in pairs.
The O2 sensor is located on the exhaust, most Cherokee's have 2 exhaust banks, so there should be one on each side of the engine. Find a wrench to fit it and screw it out, there should be an electrical connection running to it so find where it connects and disconnect it. Reverse for installation.
Sensor 1 is the sensor before the cat. converter and bank 2 is the side of the engine Cylinder #2 is on. Not sure of your specific vehicle, but I have found this to be the general rule with sensor #'s and banks.
Oxygen sensor is on the exhaust. It controls fuel injectors, and if bad will cause "check engine" and will fail at smog test. They cost about $50. I replace them every 2 years. Right and left are determined from sitting in the drivers seat. Right is passenger in the USA.
The camshaft position sensor is located under the hood, beneath the engine cover. The engine cover must be removed with a wrench to access the two sensor banks and their wiring harnesses.
The 4.0L can have one or two banks. If it has two, bank one sensor one is the sensor closest to the front that is screwed into the exhaust manifold. If only one bank it will be the only sensor in the exhaust manifold.
It's not very likely that a 4 cylinder will have 2 banks, unless the engine is in a "v" confinguration. Haven't heard of a V-4, but it's possible. Oxygen sensors for inline engines are on the exhaust manifold, just past the point where all 4 cylinders have joined. There are two . One is ahead of the converter & one is below the converter. They are called upstream & downstream sensors.
On a 1998 Mercury Mountaineer , 4.0 litre SOHC , V6 engine : Bank 1 is the passenger side of the engine Bank 2 is the drivers side of the engine There are a total of ( 4 ) oxygen sensors Sensor 1 ( on each side of the engine ) would be close to the engine BEFORE the exhaust enters the catalytic converter and is used to send a signal to the Powertrain Control Module ( PCM ) to adjust the fuel ratio for the engine Sensor 2 ( on each side of the engine ) is AFTER the exhaust has passed through the catalytic converter and is also called a catalyst monitor