i have a technical oxygen sensor question i would like to pose to the
list.  i am in the process of replacing the oxygen sensor on a engine
from a 99 golf 2.0 liter engine code AEG.  the oxygen sensor that i am
replacing is the one after the catalytic converter.  in an attempt to
cut the cost on this replacement i saw that it was a four wire bosch
sensor, so i searched the web for cheap four wire bosch sensors that
could be spliced to my wiring harness.  i found a sensor for $40 for a
93-95 chrysler concord.  when i went to change the sensor out i noticed
that it was unlike any sensor that i had seen before.

after doing some more web research i have determined that this car and all
newer vw's and audi's are using planar oxygen sensors.  the one i bought
is a four wire heated thimble sensor.  so my question is will the four
wire heated thimble work for me or do i need to buy a planar sensor, ie
what are the draw backs of running a thimble sensor in place of a planar
sensor?  from what i have read the differences are that the planar sensor
reacts faster, heats faster, and requires less current to run the heater,
but other than that it looks like the output is the same.  one other
question i would like to ask is does anybody know the bosch part number
for the oxygen sensor after the catalytic converter on a 99 golf?  mine
was pitted on the first couple of digits so i can't make out the number
and i can't find the number on the web, the long bosch part number that
is.

i've been using the bosch site to cross numbers for cheap planar sensors
and i have it down to about $61 for a planar sensor that can be spliced to
my wiring harness.  thats probably what i will do but i would still be
interested to know if i could use the thimble sensor in place of the the
planar sensor.  if anyone wants to do reading on sensor stuff here are
some links.  i've asked this question to some other lists and come up
short so i am depending on the cumulative far reaching wisdom of the
vanagon list. :)

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bosch faq oxygen sensor web site

http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/

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vw 2.0 uses a planar oxygen sensor

http://www.asashop.org/autoinc/may2003/o2.htm

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which cars use planar oxygen sensors, LSF 4 narrow band sensors

http://www.forparts.com/Bos02update2.htm

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technical pdf on bosch sensors, very good

http://www.sts.sae.org/membersonly/techinfo/servicetech/oxygen13-17.pdf

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