I have these three O2 related sensor error codes. Are they all codes for the front 02 sensor (the one in-front of the catalytic converter) ?

P1133 - HO2S Insufficient Switching Bank 1 Sensor 1
P0133 - O2 Sensor Circuit Slow Response Bank 1 Sensor 1
P0130 - O2 Sensor Circuit Bank 1 Sensor 1

My car is a Saturn Ion 2003

  • Yes, the "sensor 1 " in the description line denotes this as a pre-catalyst sensor. Dec 7, 2016 at 19:22

1 Answer 1


From http://o2sensors.com.au/static/o2-sensor-identification-and-locations :

So what is Sensor 1? Sensor 1 is the O2 sensor that is located before or upstream of the catalytic converter. (Pre-cat)

So then if your diagnostic code is B1 S2 that means Bank 1 Sensor 2 down stream (post-cat). If its B2 S2 that means Bank 2 (opposite Bank to Bank 1) and the downstream after cat o2 sensor.

Since all of your codes are bank 1, sensor 1, they are all coming from the same pre-cat O2 sensor.

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