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Old 04-01-2010, 09:06 AM
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Should have listened to tech22. No obvious vacuum leaks. Finally decided to take a stab and replace MAF sensor due to slightly unusual RPM vs. MAF sensor output signals, as viewed on a scatter plot. I was out of options.

No more P0171, but during my "learning" drive, friggin' code P1491 shows up as a "1st trip" (no SES light)!!!!

I'm sitting there at the top of the ramp going, "oh, WTF is that????"

So I get it home, all of the sensors are reporting ready, SES light is off, and I hold my breath and cross my fingers that I can get the emissions test today.

Well, I babied the car all of the way there and PASSED! When I got to work, I checked the codes with my scanner and the P1491 had been cleared, so it must have been a transient thing.

I vaguely remember my wife having this code couple of years ago, and the repair guy said she needed a new catalytic converter. BS.

Thanks to this site, I know that it's the vacuum cut valve bypass valve, which I now have a year and a half to diagnose and fix if necessary.

THANKS AGAIN to this site, the folks here, and a mea culpa for not believing that my MAF needed replacement.

I'm still wondering about the "1 bank or 2 banks" question.

Last edited by pzaremba; 04-01-2010 at 09:09 AM.
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