Jeff Strickland wrote:
> Spark plugs are old, 150,000 miles
> and 16 years (1997 vehicle).
>
> I decide to change the plugs. ...
>
> When I am done, the engine runs poorly, ... I discover the plug wire
> not seated well on the plug, easy to cure.
>
> Engine instantly runs better -- misfire is gone.
>
> Now I am driving around with the scan tool connected ...
>
> I have a Pending Code, P0430 CATALYST BELOW EFFICIENCY BANK2...
>
> So, my question is if I damaged my CAT or if it is merely a
> coincidence that I have a P0430 Code in pending status?

raw fuel will certainly damage a catalytic converter, but not
necessarily in just a few miles or days. reset the PCM with the scan
tool and drive it long distances for a few days and see if a P0430 comes
up again. And I might even do that one more time again.

The parameters to set a "cat-efficiency" code are unlikely to occur from
a bad sensor, just a bad cat-con. And the cat-con is just as likely
worn out from age and not changing the plugs 75,000 miles ago, as from
the recent "whoops" with the plug wire.

I am speaking purely of OBDII operational engine mangement theory, not
of any case-specific "known issue" on a 1997 BMW/Toyota What-ever-mobile.
GW