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Re: V8 problem possibly solved....
On 18 May 1996, Michael LaRosa wrote:
> I started her back up, pulled the heater wire connector off
> and measured for 12v from one of the 2 wires on the harness.
> Nadda, nothing, no voltage at all..... I believe their should some
> kind of voltage to heat up the sensor, yes ?
I assume you checked both wires, to make sure you were measuring the 12v
wire and not the ground wire?
Also, if the O2 sensor heater is turned on by the ECU, then it
may be a fault in the ECU, or it may be a bad wire (an open circuit).
Or, it may be that the ECU simply had the heater shut off during the time
that you were measuring the voltage. Another test would be to wire a
small light bulb inparallel with your heater, adn put it inside the car.
Then watch it as you drive. If it never comes on, then you have
diagnosed your problem.
Now for the solution, if the diagnosis is correct. First check
for bad wires, but if that is not the case, then you have a bad ECU. You
can wire the heater directly to an ignition-switched 12v source, or
replace the ECU. It may run a little better if you replace the ECu,
becuase the more exotic O2 sensor routines (I don't know if the V8 ECU is
this advanced - prolly not) actually stop sensing and measure resistance
of the heater periodically to calculate the sensor temperature. This
allows the ECU to "expand" the normal operating range of the O2 sensor a
little by knowing what its temp is.
Graydon D. Stuckey
Flint, Michigan USA
'86 Audi 5000 CS Turbo Quattro, GDS Racing Stage II