New to Audifans, 1991 Audi 80Q, bad O2?

Huw Powell human747 at
Mon Jan 27 17:42:08 EST 2003

> A few weeks ago Bosch P/N 13913 [OXS] was installed, ran fine for a week or so but
> then began cutting real bad, pressing gas pedal did nothing, but could
> always restart quickly and would wait 5 seconds until the symptoms came back
> whenever car went into closed loop and started monitoring O2 output (would
> be ok on a cold start till it warmed up for a little while), I learned that
> unplugging the preheat connector under hood would cause the problem to
> immediately disappear but getting into the problem further, I noticed for
> some reason that the preheat isn't optional for me, after driving for 15
> minutes without preheat connected it still wouldn't throw anything but .5v
> telling me it wasn't hot enough yet.

Disconnecting the heater should not afect function at all, except maybe
slightly extending the time it takes to get up to temperature.

This was a sensor you spliced into the original plugs, right?  I suspect
the splicing of perhaps having a short to ground (one of the heater
wires), or worse yet, 12 volts (the other heater wire).

.5v doesn't mean the OXS is not warmed up, the ECU of the car actually
has a reference voltage at that terminal of .5 v, can be measured if the
OXS is not connected, for example, as I recall.

You *may* have a bad sensor, of course - but the splice is a more likely
culprit.  Take a careful look, see if it is still good, see if the
wiring is caught or chafing (it could rub the front axle and become
de-insulated pretty fast)

> So, have I learned that the sensor is officially bad and the preheat is
> either short circuiting to the signal lead inside the sensor/the sensor
> throws wrong voltage intermittently when heated or is something else causing
> the problem?

Huw Powell

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