P0171 and P017n Was: What tools do I need? (P0420 Bank 1 catalytic inefficiency on a 15 year old dual-cat vehicle)
Oh, another thought on this old thread..... something that should always
be checked if it's not your car: if you're seeing O2 sensor readings that
are super-rich, especially if they are consistently rich on all sensors,
make sure the engine grounds are good. Missing engine ground cables and/or
severe rust can cause sensors to wind up with a poor ground reference and
then you get bad sensor values.
The original poster's engine didn't sound like that sort of issue but it's
a good idea to spend a minute doing a visual check of grounds no matter what
you're looking at.
--scott
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"C'est un Nagra. C'est suisse, et tres, tres precis."
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