|Tech Article Title
Sensor Replacement (B6 1.8t)
Background: I was getting a racing fan (sounds like a
leaf-blower) at start-up on my 2002 1.8t. Eventually, it threw a solid
CEL, and the code pulled was 16502: Engine Coolant Temperature Cicuit,
(G62): High. Due to ECU connectivity problems, my dealer couldn't warranty
this repair (for some reason they couldn't connect to my ECU, and it had
nothing to do with my REVO.) So...I decided to tackle it myself. I have
also heard that this sensor can make the coolant gauge either not work or
be very erratic, although I didn't have this problem. I found write-ups
that I believe were for the B5...but it seems MUCH harder to get to on the
B6, so I decided to do this write-up.
Parts Needed (can get at any
Audi or VW dealer):
Temperature Sensor: 059-919-501-A (make sure it's
O ring Seal: N-903-168-02 (highly recommend you replace
this...mine was very dry and cracked...may want a couple in case you drop
one and it lands on the transmission and you can't get it out)
retaining clip: 032-121-142 (breaks easily...may want a couple just in
About $7-$10 in parts:
Small flathead screwdriver...I found this the best method for
removing the retaining clip.
Beware...this is a serious knuckle
banger to get to the sensor and the clip...even if you have average size
Make sure the engine is dead COLD before doing this...or
you'll get a coolant surprise right in your face. Remove the coolant cap
to remove any back pressure, and then replace. This will minimize to
eliminate any coolant coming from the sensor socket.
Here is the
location of the coolant temp. sensor...It is at the rear of the block by
the firewall...it is somewhat hidden by the wiring harness, but you can
just make out the top of the wire clip (inside red circle).
is a picture of what you need to do to get to that sensor...I actually had
both hands back there. I removed the clip to the fuel line as it was
destroying my arm...covered the bare metal bracket in duct tape as it was
a tad sharp.
sensor is held into a vertical tube with a plastic retaining clip. If you
feel back there, you can feel the sensor going into the tube, and just
below the tube, you can feel a plastic clip sticking out towards the rear
of the vehicle. This clip should move back and forth a tad. Now...this
clip needs to come straight off, or it will break. I couldn't get my
thumbs back there for any grip, so I used a small, flathead screwdriver to
pry the clip to it's first "pop", then was able to pull it the rest of the
With the clip removed, pull straight up on the sensor to
remove. You may hear a suction type noise when doing this, and don't pull
by the wires. The wiring harness is long enough to pull the sensor out
into the open so it's easier to work with.
the wiring harness clip, and remove the old sensor. Grab the new
sensor...and push into the wiring harness until you hear a "click." It can
only go on one way. For those needing a picture of this:
you can do one of two things with the O-ring: You can put it on the sensor
first, and then put the entire thing into the tube, or you can seat the
O-ring into the tube (yup, more knuckle banging) and then push in the
sensor. I tried the first way, got the car all together, and then the
sensor popped out once the car got hot and spewed coolant everywhere. Here
is a pic of the O-ring on the sensor:
the sensor into the tube and make sure it's fully seated. If it's not
fully seated straight up and down, the clip will not catch the sensor and
you'll have a mess when the car gets hot.
With the sensor in, now
comes the hard part...The plastic retaining clip has to go straight on. It
goes around the tube that the sensor is in, and the inward tabs on the
clip go into little slits on the side of the tube...you can actually feel
these slits. This clip is what keeps the sensor from coming out, so it the
sensor is too high, you'll miss the lip on the sensor that the clip rests
on. This may take a few tries and a little frustration, but you'll get it.
Once in...give a few test tugs on the sensor (NOT the wires) to make sure
it's in there.
Put everything back together...turn on car, let it
idle to warm, and road test. Good luck!
DISCLAIMER: This write-up
is created for the purpose of benefiting Audi owners everywhere. I take no
responsibility in any damage that may incur while attempting the steps in
these paragraphs. I am not an Audi technician nor was I supervised by one.
Please perform this at your own risk. If unsure or uncertain, please do