My check engine light has been coming on lately, so I ran the codes. Heres the list:

• p0133 O2 Sensor Slow Response (Bank 1 Sensor 1)
• p1131 Lack of HO2S1 Switches-lean (Bank 1 Sensor 1)
• p0171 System too Lean (Bank 1)
• p0420 Catalyst System Efficiency Below Threshold (Bank 1)

I'm assuming that an O2 sensor is kaput, but could that be causing all those codes?. Also, my chiltons manual is worthless about identifying which sensors are where. Is bank 1 sensor 1 pre-cat on the right?

On another note, my car has started 'chugging' lately. It feels like the engine misses. It happens when stopped and while driving. Is this bad spark plugs, wires...or bad fuel mixture from dead O2 sensor?

BTW 2.5L v6

Originally posted by ApocGold:

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...On another note, my car has started 'chugging' lately. It feels like the engine misses. It happens when stopped and while driving. Is this bad spark plugs, wires...or bad fuel mixture from dead O2 sensor?

BTW 2.5L v6

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Yes, it could be from a bad Bank 1 (firewall side) upper O2 sensor.

Change that first and see if it helps.
Bank 1 Upper O2 sensor how to from Duratec Maintenance FAQ