FC 45

[David A. Cooley]

>
> That's interesting.  I had a bad O2 on my GN last year
> which caused me to fail the emissions check.  I replaced
> it with a Bosch and with a little tuning, I was able to
> get my emissions down to 6 pmm of HC. Max allowable is
> 220 ppm.  Before the sensor change it blew something
> like 330 ppm.
>
> Maybe the Bosch sensors work fine on the older C3 ECMs
> but not the newer P4s ?

It's the 3 and 4 wire heated O2's that have the problem... The 3 lead, they
ground the heater to the shell, but the units where the O2 sensing element
has 2 wires coming out is the problem child.  GM expects the low side to be
tied to the shell and bosch isolates it.