Error codes

2006 KIA SPECTRA
120,000 MILES • 4 CYL • 2WD • AUTOMATIC
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CINDI KING
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  • 1 POST
Cannot pass California smog test. Have error codes 0171, 0121and 0420. In that order. Help!
Oct 6, 2017 at 8:54 PM
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STEVE W.
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 15,146 POSTS
P0171 - System Too Lean - Bank 1.
P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem.
P0420 - Catalyst System Efficiency Below Threshold - Bank 1.

Needs to be put on a good scan tool and check the operation of the O2 sensors as well as the TPS under running conditions.
The codes suggest that you may have a vacuum leak and a faulty TPS. But without proper testing you would not be sure.

The P0420 code could be an O2 sensor issue but it could also be a failed converter.
The same testing to look at what the sensors are actually doing would show you which.
Oct 6, 2017 at 9:16 PM
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