[s-cars] CAM SENSOR ERROR

[Igor Kessel]

This is a multi-part message in MIME format.
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DDDOHIO at aol.com wrote:
>
> --
> [ Picked text/plain from multipart/alternative ]
> Can anyone help please..... I have a 1995 S6 that I have been getting a
> "check engine" light intermittently. The car does not run rough or in any
> other way seem like anything is wrong except that the light is on.....till
> you stop and shut off the engine. The car will crank but not start. After 4
> or 5 hours of sitting the car will then start (like it has "cooled down" or
> something has reset) It is leaving a "cam sensor code". My mechanic thinks
> the cam sensor is either good or bad....not intermittent and tells me he is
> hesitant to replace it because of the $395.00 price. On one occasion I was
> driving and the check engine lite went on and I headed for home to park the
> car for the 4 to 5 hour "rest period" and on the way home the lite went out.
> When I got home the light was still out so I turned the engine off and tried
> to immediately restart it and it fired right up. I am afraid to drive the car
> anywhere for fear of being stranded for a 4 to 5 hour period.
>
> Has anyone ever heard of such a weird problem and any suggestions???
>
> Thanks,
>
> Dave Dinning
> Westerville, Ohio
> 614-204-9536

Dave,
it is the cam sensor, it is intermittent, it is in the wiring, and it is
always like this.
See the attached file from my archive. I can confirm the info with my
own BTDT.

--
Igor Kessel
two turbo quattros
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Rod, I changed mine recently. I never had any idling problems. It was always
Hard/No start condition and progressively got worse until it was "No start"
pretty much all the time. Only got Fault code 2113. I think when the sensor
fails the ECU retards the timing by 6 degrees or something? Basically once
the car is running it will keep running if the sensor fails, just don't shut
it off...

Dave is right, it's a 5 min job... once you pulled the timing belt and cam
sprocket ! (of course that's the hard job isn't it). I was able to do the
whole job without having to remove my bumper or radiator. Everything is
pretty straight forward (follow parts of Fred's instructions on Urs4), the
only difficult part for me was removing the cam sprocket. You'll have to
find a way to secure it while you torque the bolt out. The piece that
triggers the CPS is known as an "Impulse Rotor" and it's attached behind the
Cam sprocket, you can get the CPS for about $90 US (I got mine from
http://www.germanautoparts.com/ <http://www.germanautoparts.com/>  ).

A few tips for troubleshooting:

Check Scott Mockry's site, you'll find a simple way to check with an LED
connected to the sensor to ensure it's working.

If you have a multimeter you can test the resistance. I also found that the
resistance between the terminals was Open except in fault mode where the
resistance was in MegOhms, I never saw resistances in the ohms range.
Needless to say when Cylinder 1 (Impulse Rotor Window) is in the sensor
'zone' then the resistance between the +5v and the switched 5V will reduce
below the open circuit position.

A site that explains the outputs is as follows
http://www.picotech.com/auto/audi.html
<http://www.picotech.com/auto/audi.html>

A scope (if you have access) on the output of the sensor might show it was
out of phase once the engine heated up if the sensor is bad, I'm not sure if
this will cause idling problems...never heard of that being a symptom.

I have digital pics of the replacement job, if you want them just let me
know.

Cheers, /James.
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Subject: RE: [s-cars] Re: Cam position sensor question
Date: Thu, 28 Mar 2002 08:30:58 -0500
From: Robert Pastore <rpastore at animalfeeds.com
To: 's4audinut' <s4audinut at aol.com, s-car-list at yahoogroups.com

I had the pleasure of changing my the cam position sensor on my 95 S6 Avant
two days ago!

When I removed it, I found the harness had been pinched between the sensor
itself and the head, and one of the wires was broken at the pinch.   What is
really strange is that the car ran for so long like that, and the problem
appeared only as "NO Start" when cold.  I understand that the ECU will give
the car a default signal and the car will keep running if the sensor fails
while it is running, but it won't start with a failed sensor.

The install isn't as bad as you might think -- remove the upper lock plate,
serp belt tensioner, then timing belt cover.   Remove cam pulley with t-belt
attached. (I used a twist tie to tie the t-belt to the pulley to sop I
wouldn't need to worry about t-belt timing.)  The sensor is behind the cam
pulley, and installs with two 5 mm socket head screws. loosen t-belt
tensioner and re-tension the belt when you put it back together.  The entire
job was under 2 hours.  The hardest part is the limited clearance
(w/radiator) for the three 6mm  *SERP BELT* tensioner bolts.  I used a 1/4" drive
ratchet for the top two, and an allen wrench on the bottom bolt.  With the
lock plate removed, the upper radiator mount is also removed, so you have
some play in the Radiator and can get those bolts out.


The sensor I removed is good, except for a bad wire.  If you'd like to
resolder the 3 wires form yours onto mine, it might be a cheap fix.   I
think the sensor cost me $165, but finally my cold start problem is solved!

Bob
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-----Original Message-----
From: s4audinut [mailto:s4audinut at aol.com]
Sent: Wednesday, March 27, 2002 10:17 PM
To: s-car-list at yahoogroups.com
Subject: [s-cars] Re: Cam position sensor question

Code says cam pos sensor, did it cause idle problems on your, car
runs like a scalded dog otherwise.
Rod
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--- In s-car-list at y..., "forgied" <forgied at d... wrote:
Rod and S-gruppees:  Gosh. Something technical that I actually know
about and can contribute:

The Cam Position Sensor (CPS) replaces the Hall sender in the 3B -style
engines. It is very small, about the size of a MoJo candy with some
wires sticking out of it.  As you suggested, it lives behind the cam
drive sprocket.  I presume that something in or attached to the cam
sprocket triggers the CPS as it goes by.  This creates a signal that is
sent to the ECU to tell the ECU where the heck them thar pistons is at,
all flying about, up and down, down and up. All real fast like too.

So if your CPS (aka "fridge magnet") gets flakey and doesn't
consistently produce the right signal and the right time, the ECU is
going to get real confused as it no longer knows when the ignition
timing and fuel injection should be triggered.

Replacing the CPS is probably about 5 minutes - after you have pulled
the timing belt and the cam sprocket.  I paid CDN$280 for the CPS and
did the timing belt and water pump while I was at it.

Check the codes if it says CPS - change it and move on.

Dave (bronzed CPS fridge magnet) Forgie
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 --- In s-car-list at y..., "s4audinut" <s4audinut at a... wrote:
I have been experiencing an idle problem with my car since I had the hot
engine installed and I am looking to cure it before I go to a big MAF or
an aftermarket ECU system (Autronic). I know it is not chip related.

The problem (as it started) is that the car wont hold idle w/out dying
unless I feather the throttle. I was getting 2 codes, one was oxy sensor
and the other was Cam position sensor also car was throwing a check
engine light. I was running adequate fuel per A/F meter and the exhaust
temps were staying in line. I replaced the idle stabilizer valve and
things improved somewhat but it still died. I then replaced the oxy
sensor and things again improved, no longer dies all time, just at early
startup, but it still exhibits a very lumpy and burbled idle. I am still
getting the check engine light and since replacing the Oxy sens. and ISV
the light remains on. I think only 2 things could be causing this, the
idle switch on the front of the T-Body or a cam pos. sensor. If you know
what is involved in replacing the CAm sensor you know why I want some BT
data, in my car you have to pull the timing belt, remove the cam gear to
get to the sensor, a good 2 hr job for even an experienced Audi tech. Do
the symptoms that I have described lead me to beleive it is truly a cam
sensor problem (codes can be wrong) or should I put a new throttle idle
switch in the hopes that it will help avoid the bigger job. I already
have abt. 270$ in the 1st 2 parts and havent priced the idle or cam
pieces, but I am getting tired of surrounding the problem, I want to fix
it. Please share informed experience with me. The dealer (Asshole Audi
of WV) wants 500$ to do the cam sensor with me providing parts because
they feel they have to take the front end off to do it (idiots). I am
very hesitant to do this because 1 it isnt necessary (I dont have a belt
cover (or room for 1)) and 2 everything radiator/A/C
condenser/Intercooler and brackets etc. are all custom built and they
will fick it up beyond repair from my experience. I have a good tech
(Chris Smith) around Cleveland who will do it for 100 $ but he is a 4 hr
drive away. Pls. help.

Rod
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