Temp Sensor for Cold Start Valve on MC2 200Q

[l.leung at juno.com]

Thanks Phil,

I finally had enough time to get into my Bentley to
determine exactly what you said, the CSV is run by 
the ECU only, no separate sensor. From what I read, 
it appears that the ECU gets it's info from the coolant
temp sensor (front of head) and then decides whether or
not to fire the CSV. Using the Output Tests, I was able
to fire the CSV, so at least electronically, all is well
there. Both the Bentley diagnostics and the results of 
the output tests seems to be pointing in the direction of:
A) bad coolant temp sensor, although it seems to be 
reading in range with a Multimeter. I tried swapping with the 
coolant gauge sensor in the flange, still hard start and
rough idle, i.e. no improvement.
B) bad coolant temp sensor wiring (unfortunately, the most likely
culprit, I think)
C) Bad CSV (if the above wiring checks out)? Do they typically
fail at around 200K miles (320K km?)
D) or bad ECU, although quick code check says it's 
all okay, 4444. That was with an essentially unrun 
engine, so I know that's really not valid.

Seems like all I need is the time to trace the wiring
(not too likely for the next couple of days). 

Any other thoughts? 

TIA,

LL - NY



-------------------------------------------------------------------
>Date: Mon, 13 Sep 2004 05:30:17 +0200
>From: "Phil Payne" <quattro at isham-research.com>
>Subject: Re: Temp Sensor for Cold Start Valve on MC2 200Q
>To: <quattro at audifans.com>
>Message-ID: <001c01c49990$05c42ee0$0700a8c0 at KMSITLTD>
>Content-Type: text/plain;	charset="iso-8859-1"

> Looking for advice as to the location of
> the temp sensor that activates the cold
> start valve on an 89 200Q, MC2 engine. Is
> it on the coolant flange neck, on the side
> of the head or the rear of the head (although
> I still can't seem to find one back there)?

It's an ECU function on the MC2 - have you tried Scott Mockry's site?

You can mess around here.  The PO of my Type 44 had an alarm light on top of the binnacle.
I've replaced this with a flush-mounted pushbutton connected with the diagnostic plugs in the
footwell, and I got the proper insert for the eyebrow dashboard from Audi to give me a "check
engine" light.

This lets me operate the CSV manually from the driver's seat.  Press the button and switch on
the ignition, then you can step through the diagnostics until the CSV fires.  I used this
trick to start another Type 44 yesterday - I was quite surprised that the MAC14 fires the CSV
10 times - the MAC12D (ur-quattro, MB engine) will only fire it 5 times.

-- 
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803



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