2003 C4S O2 sensors

[kpl]

Seems like I get a different results on different parts house websites. What are the part numbers for the 02 sensors? I might as well get the numbers for the cats too in case they are shot.

Thanks for your help,

[Loren]

For a 2003 C4S:

2 sensors before the cat (one per side) - 996.606.168.01 -- US MSRP $330.15 each

2 sensors after the cat (one per side) - 996.606.178.01-- US MSRP $330.15 each

996.113.031.06 Catalytic converter -- US MSRP $2218.16

996.113.032.06 Catalytic converter -- US MSRP $2218.16

[kpl]

Thanks! Which cat is considered "bank 1"? I got a check engine light P0420, swapped the O2's side to side, and the same code came back, so it's got to be the cat.

[JFP in PA]

Thanks! Which cat is considered "bank 1"? I got a check engine light P0420, swapped the O2's side to side, and the same code came back, so it's got to be the cat.

The best way to determine if a cat is toast is by looking at the O2 sensor voltages before and after the cat, if the sensor voltage after the cat remains fairly constant while the voltage for the sensor before the cat swings back and forth, the cat is good. If the voltage for the sensor after the cat follows the pattern for the sensor before it, the cat is gone: