Can the O2 sensors be installed incorrectly on a 993?

[earossi]

I am in the process of re-installing my 3.6 motor in my 98 993 and just realized that I may not have properly marked the O2 leads when I disconnected them at the connectors on each of the fender wells in the engine bay. So, I have a couple of questions, since there are (4) O2 sensors involved (2 for cyl1-3 and 2 for cyl 4-6):

1, Can the O2 sensors be mistakenly interchanged upstream and down stream of the cat? Or, are the connectors on the ends of the sensor leads different? If so, can someone provide information to make certain that I have the correct sensor installed in the correct bung on the cat.

2, And, if the answer to #1 is that the connectors are the same for both sensors…..then how do I identify which plug to install on the upstream and down stream sensors? Obviously, I will have ECU issues if the O2 sensors are reversed in the wiring.

Normally, in similar situations, Porsche has been very good about color coding or in shapes of their connectors to prevent errors in installing them…..but, for the O2 sensors…….I don't see any difference between the sensor connectors for the upstream or downstream side of the cat…..other than the fact that the sensors have different part numbers. But, what is there to keep me from mistakenly reversing the connections?

I just want to be sure.

[911pcars]

Would it just be a matter of looking up the replacement parts at any parts source (e.g. Pelican Parts) and comparing front vs. rear sensor numbers? If the same number, they're interchangeable. If different numbers ..........

Sherwood

[earossi]

Originally Posted by 911pcars

Would it just be a matter of looking up the replacement parts at any parts source (e.g. Pelican Parts) and comparing front vs. rear sensor numbers? If the same number, they're interchangeable. If different numbers ..........

Sherwood

Thanks for the response. I think that my posting may be confusing. There are two oxygen sensors on the left and two sensors on the right side of the engine bay. Each pair consists of an upstream and a downstream sensor (relative to the cat). Which connector on the left and right receives the wiring from the upstream or downstream sensors? That is what I am trying to determine, since I did not correctly identify these connectors when I disassembled the car.

[jhg41977]

Arent the leads different lengths? I dont think they will reach if you install them in reverse order. Good news, you can replace them while the motor is in, so not a problem if you find out they are reversed.

[earossi]

Yes, the leads have different lengths and I have them installed in the cat correctly. The issue is that the plugs on the two sensors can be plugged into either of the plugs at the other end. How do I know that I don't have them reversed there?

[jhg41977]

Are you certain the ends are identical? I thought one alignment pin was slightly different. If not, Im in the same boat as you since I did not label mine either.