In a message dated 96-05-29 11:13:34 EDT, raven@halcyon.com (Mark McCulley)
writes:

>I'm puzzled. Why does the Vanagon's O2 sensor need a heating element if it
is
>sitting in the catalytic converter which is quite hot?
>
>
>

The heater is needed to get the sensor up to operating temparature long
before the exhaust gets hot enough.  It also helps when the engine idles for
long periods as the cooler exhaust at idle will often let the sesnor cool
down too much for it to operate.  With the digifant, it is extermely
important that the sensor always gives a relaible signal.  If the sensor
output drops off, then the computer will continue to richen the mixture until
the sinal returns.  If the sensor works intermiaantly, then the mixture
richening process will run away until there is no power and you actually get
black soot out of the exhaust.

Dennis.