What is involved with changing all 4 O2 sensors? Can it be done without taking off the muffler?

 

I've swapped my exhaust out a few times, changing the sensors without pulling off the exhaust might be difficult. I think you can gain access to the sensors if you remove the rear bumper and some other hardware, but at that point, you might as well remove the exhaust. It is a straight forward job, an extra set of hands helps quite a bit as it is a bit to handle by yourself. Hope that was helpful.

Justin

 

Whoa... you don't have to take the exhaust off at all. Just remove the bumper cover and intercoolers and you are there. I have a DIY for changing the spark plugs here (4th picture from the right on second row shows the sensors): http://www.comtech.ws/Porsche911/DIY/Plugs/

You might as well change the plugs while you are in there though. The first time it took me 3.5 hours. I can do it now in about 30 minutes.

 

I'll be using your writeup when I do my plugs and possibly to resolve my camshaft issue slider. I have not gone through the steps yet, but after reading through it, I got the impression that taking off the exhaust alone was a bit easier and less parts management, than going through the bumper. Either way, I'm sure both should be straight forward DIY jobs.

Justin

 

I replaced all 4 O2 sensors on my car without removing either the bumper cover or the muffler. It would have been easier to do if I had lowered the motor a bit by loosening the bolts on the rear motor mounts, but I actually didn't do that either. You do need an O2 sensor removal wrench. I borrowed one from my indie to do the job. Here are the steps:

1. Lift rear of car and set on jackstands

2. Support motor at center with jack, loosen the 18mm bolts on the motor mounts, and lower the jack onto a support. You only need an extra inch or so to get your hands some room to work. There's a DIY here or on rennlist describing this procedure. Like I said, I didn't do this, but it does make it harder to get your hands above the cats.

3. Unplug the O2 sensors in the engine compartment and snake the wires through.

4. Put O2 sensor wrench on old sensor and remove. (Hope that they were installed with sufficient anti-sieze - mine were.)

5. Be careful not to slop anti-seize on the new sensors, and install. Also be careful not to mix up the pre-cat wideband sensors with the post cat sensors.

6. Snake wires back up and plug in. Raise motor on jack and tighten the motor mount bolts to proper torque.

It's a bit of a PITA, like anything on this car, but really not all that difficult.

FWIW, Kevin had me do this after I installed his Stage 2A kit as well - I think it's his standard practice. He really should have you do it when the motor is out, but I think he likes to make you suffer.

Jon

 

The front (pre-cat) O2 sensors are 5 wire Bosch #17044, the rears (post-cat) 4 wire Bosch # 16205

 

Is there any way to tell which of your O2 sensor(s) need replacement when the CEL illuminates? Is it simply assumed to replace all four (if one is going bad they are all likely to be going bad?)

 

If you connect a obdII and you have codes showing it will tell you which bank , bank 1 or 2 each side is considered a bank

 

The codes will tell you which sensor (pre- or post-cat, and which cylinder bank). The pre-cat sensors are used to measure air-fuel ratio, and are used for engine control. You have to have them in good shape for the engine to run properly. The post-cat sensors measure cat efficiency, and are there strictly for pollution control compliance measurement. Sometimes the post-cat sensor error indicates a problem with the cat, rather than the sensor itself. The pre-cat (wideband) sensors are a lot more expensive than the post-cat ones.

There are some tunes that turn off the CEL from the post-cat sensors, and some workarounds to fool the sensor. Not advocating that, just information.

Jon

 

so bank 1 is before cats and bank 2 is after cats?
or bank 1 is driver side and bank 2 passenger side?

 

bank 1 is drivers side...

 

thanks Mark