Oxygen sensor replacement
Parts needed:
Tools needed:
Open engine compartment and unplug the Oxygen sensor. The
connection is on the left side of the engine compartment,
at a place where several wires are held down with a flexible
metal clip. It is a 3-inch long, 1/2 inch diameter black
connection. The wire is black on both sides of the connection
(as opposed to the other grey wires you will see there).
Jack up the car on the driver's side and remove the
left rear wheel. On the catalytic converter you will see
a small metal guard plate that covers the outside and bottom
of the catalytic converter. This should be removed (about
six 10mm bolts).
The O2 sensor should have a small half-cylinder metal guard
on it. Remove this by pulling it away from the car. It is
held on by a small (but quite stubborn) metal clip. Moving
it side to side and up and down seems to help, as oppsed to
just pulling it straight out. Put some Liquid Wrench
on the base of the O2 sensor unit and allow it to soak in.
Carefully pry out the rubber grommet that is in the wheel
well where the O2 sensor wire goes into the engine compartment.
A flat-headed screwdriver should do the trick. You should now
be able to pull the entire 1.5 foot wire out through the small
hole. Cut the three wires at the O2 sensor unit as close to
the O2 sensor as possible. If you are not using the official
factory part, carefully label one of the white wires on the
"outside" of the grommet, and label the matching wire on the
"inside" of the grommet. You will be cutting the wires, and
will need to know which to match up correctly.
Either use a deep 21mm socket, or the large (and I do mean large)
open-faced wrench to remove the O2 sensor. This will most likely
call for fitting the wrench onto the unit and using a mallet
of sorts to loosen the sensor. The catalytic converter gets
extremely hot, and makes for a tough time of getting anything
unthreaded. Once it has been loosened, however, removal should
be easy.
If you bought the official Porsche factory part, you can skip
the next few paragraphs. However, if you bought the generic
Bosch O2 sensor, read on. Note: Bosch supplies Porsche with
the original sensor unit anyways, and both are completely
identical. The only difference is $150 and the connecting
plug and wires (covered in the following few paragraphs).
This work can be done inside in a shop, or someplace where a
soldering gun can be used safely. Take the old O2 sensor
and wire, which has had one of the white leads marked in
a couple of places, and cut all three wires just "inside"
the grommet (by that I mean on the side that was inside the
engine bay). Be sure that one of the markings you made on one
of the white wires is on either side
of this cut, so you know which goes where.
Then slip off the small (4 inch) black tubing
that covers the wires on the sensor side of the cut.
Determine where exactly the marked white wire goes into the
sensor. Then take the new sensor, and mark the corresponding
wire by following it from the top of the sensor up throug
the black tubing. This way you'll know which wires to
solder together. See the digram for a layout of the three
wires. One of the two white wires must be marked they
can be distinguished.
Cut off the plug on the new generic sensor. This plug
won't fit, and is useless. I cracked the plug open so
I could cut the wires closer in, and get another inch
of length. You should now have two main pieces:
a new sensor with three
5-inch wires coming out of the top (with one of the
white wires marked), and the original
plug with three 1.5 foot wires (with the corresponding white wire
marked).
Now slide the grommet onto the new sensor wires, down
to the edge of the black tubing. There should be about
4 inches of black tubing covering the three wires.
Put three pieces of heat shrink tubing over the old wires,
and solder the matching wires together. Slide the heat
shrink tubing over the soldered connections and warm
appropriately for them to shrink. Now cover all three
wires together with some electrical tape. You should now have
one large piece: Starting with the old three-pin connecting
plug, followed by about 1.5 feet of wire , your new soldered
connections, the grommet, then about 4 inches of wires,
then the new O2 sensor.
Remove the little plastic guard cap on the new O2 sensor
and screw it into the opening on the catalytic
converter. Tighten it down sufficiently with the
open-faced wrench (note that a socket will not work now
because of the wires).
Thread the wire through the hole into the
engine compartment, and carefully push the grommet
back into place. Again, a flat-headed screwdriver
might help if used carefully.
Connect the O2 sensor wires inside the engine compartment.
Replace the sensor shield, the metal guard on the cat converter,
and the wheel. Start the car and enjoy!
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