My check engine light came on and I had the codes diagnosed at
Autozone (Catalyst System Efficiency Below Threshold Bank 1 and 2).
Any ideas on what could be causing this. The light came on once and I
disconnected the battery and shut the light off but it came back on in
about 20 miles of driving. Would it be unusual for both converters to
fail within 20-40 miles of each other. Thanks for any advice.
I had this problem with my 1996 Tbird 4.6 at ~120k miles (now at 145k).
Mine didn't both start acting up at once though. When #2 started
acting up, I just kept clearing it and it was ok for about 10k-15k the
first time. The milage between problems decreased until I was resetting
it every day. I then started noticing that #1 was acting up. I took it
in to the dealer and they said it needed a new head pipe assembly
(contains a preconverter for each side of the engine and the main
converter)- and they could get it done for about $1600.00 - well,
needless to say, I jumped right on that- NOT. I had a cheap (not steel-
a less durable metal - aluminum perhaps) one put on at Midas for about
$950. Note: in these figures only $150-$200 is labor, the rest is for
My car sounds like crap now- you can definitely hear the difference in
the exhaust system- but at least it will pass inspection and it runs
without check engine lights or the 02 sensors killing the engine.
Moral of the story - check everything else before you look at a new cat-
they're expensive, and at least in my case, the car is not the same
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