How do you get the connector for 1999 Quest o2 sensor off?

[Daiyoshida]

Every article on o2 sensor replacement says getting the sensor itself off the exhaust manifold is the hard part. Not mine. I put WD40 on it and left it overnight. It came off easy the next day.

The hard part is trying to get the connector to come apart. The connector is attached under the front of the engine and had a plastic clip over the sensor side wires. I took the clip off and it exposed 3 wires going into the connector but I don't see any visible means of getting the connectors apart. To make matters worse, if I go at it from under the car the beam that the connector is attached to is in the way. I go from under the hood, the fan housing and everything else is in the way. I can't believe I'm stuck not being able to finish this simple job because I can't get the connector off.

Anybody here have have experience with this type of connectors? I would really appreciate some input on this matter.
The vehicle in question is a 1999 Nissan Quest.

Thank you in advance.

[superuber]

Your right, that is usually the easiest part. Some connectors you actually have to push on a tab, then pull. Not sure if thats the kind you have? It really shouldnt be that hard. But you really need to be able to get close to it to see what your doing.

[glennbuskirk]

I had the same problem and question, before Google led me to your post. Background is, my 1999 Nissan Quest was throwing a P0135 code (in addition to a P0235). The P0135 indicates the heater circuit in the upstream O2 sensor. The fuse for the O2 sensor was intact. I jacked up the frontend of the van securely (with the low body panels, I couldn't drive up onto my ramps). I found the upstream O2 sensor to be most accessible from under the front of the vehicle. It is easily visible from under the hood, but the fan cowling prevents access with my big hands and arms. I ordered a 7/8" Oxygen Sensor wrench from Amazon for about $6, but I could have borrowed one from Autozone. It used a 1/2" ratchet/breaker bar. The Oxygen Sensor socket has a cutout slot to pass the sensor's wires through. My breaker bar gave me about 12" of leverage, so sitting in front of the vehicle I was able to grasp the lever and apply some muscle; The sensor broke free without having to preheat or apply a penetrant. However, I was unable to separate the electrical connector of the sensor. The connector housing on the sensor side has two plastic fasteners that push-in to holes in a rigid metal part of the vehicle. This has to be removed anyways, so we took a sturdy screwdriver, and pried the connector assembly away from the metal part. This destroyed the plastic fasteners, but they're part of the bad sensor assembly anyways. Now we were able to pull the connector assembly down for more visibility, and to find and manipulate the locking tab (which was on the side toward the plastic fasteners). We were able to separate the electrical connectors. The replacement OEM sensor assembly was ordered from Autozone for about $54. I will install it today (Won't forget the anti-sieze compound!).
Hopefully this will take care of the P0135 and the engine will run smooth. BTW, these codes appeared a month or two after replacing the distributor with a new Richporter part. I'm going to ignore the P0235 anti-knock sensor code, which I understand will not light the CEL by itself.