[V6-12v] all quiet on the AUDI Front

[Tom Christiansen]

James,

>2. Audi tech told me they had found nothing except (sic.) an 'intermittent
>non-signal from one lambda (O2) sensor. I said - "Well, don't you think the
>cause of my intermittent hesitation could be an intermittent non-signal?" 
>"Well,
>maybe," he said, "but we usually replace the Coolant Temp Sender first 
>because
>they're usually the only thing that can go without leaving a permanent fault
>code."

There is a code for a faulty ECT. 2312 (AFAIR). There are a few conditions 
which will trigger that error code (and turn on MIL):

1) Wiring fault (short to GND, B+, broken wire).
2) Faulty sensor (indicated temp hasn't risen to above 70 deg C after 18 
minutes).
3) Thermostat stuck open (causes coolant temp to stay low).

>3. Tell me how to do the following:
>a) if my manual tells me to 'check for an open circuit between connector X
>and connector Y, what setting do I use on a multimeter? Resistance? 
>Voltage? If
>resistance, what kind of reading would be good and bad for an open circuit?
>b) if my manual tells me to check for a short circuit, same question as
>above...
>c) if my manual says to check for an earth fault between connector X and
>'engine earth', same question again...

All of above: Use the resistance setting on the multimeter.

If the manual tells you to measure a short between X and Y, you stick one 
test lead on X, the other on Y, and the meter should read 0 ohm. When 
measuring short circuits you'll never get 0.000 ohm exactly as the 
resistance of the test leads and, more importantly, the connections between 
the test leads and the device under test will me measured as well. If it's 
less than 1-2 ohm, I'd call it a short - at least for signal wires. When 
measuring heavy gauge wires (battery cables, starter cables, etc) I'd 
expect to see a resistance of roughly that you get when shorting the two 
test leads together (typ < 0.5 ohm).

If the manual tells you to measure an open circuit between X and Y, you 
stick one test lead on X, the other on Y, and the meter should read 
infinity (or overload).

>d) does anyone have a procedure, or any warnings, about disconnecting the
>multi-pin connectors to the ECU in order to test the wiring between the
>connectors in the engine bay and the multi-pins in there? Also how does 
>one check the
>continuity - do you need a multi meter with bloody great long leads, or is
>there a way of extending them reliably?

The leads typically have banana plugs on them. Get a long banana plug wire 
and use it to extend one of the test leads. It's plug-'n'-play. No need to 
cut wires here. You can make your own banana plug wire by getting two plugs 
at an electronics store and connecting them with a piece of wire of 
suitable length. The connectors are hermaphrodite types. They look like 
males, but have a hole in them enabling two connectors to be connected. Use 
a stranded 14-18 gauge or so.

I wonder if your problem could be caused by dirt in the throttle 
potentiometer... When pots fail they'll typically open intermittently on 
the wiper connection, but if you turn the shaft back and forth, they regain 
contact. It's a longshot, but it does make sense based on your description 
of the problem... But I've never cured a hesitation problem so I'm guessing 
here.

Tom