"Geoff Welsh" > wrote in message
...
> 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


I have reset the P0430, and the code has returned. Several short trips,
that's my normal driving profile. I sometimes will drive for 30-ish miles
one-way, but generally my trips are shorter.

I would not have thought that I could damage the CAT in the time it took to
have the P0306 MISFIRE CYLINDER 6 move from the Pending column to Active.

I'm okay with theory of operation over practical application.