P0133 Code Mystery New O2 Sensor

[coachcrow56]

I replaced my O2 sensor (upstream) on my 2000 GTP Saturday morning---drove car about 50 miles and Service Engine Light comes on---code P0133----slow response Bank 1 Sensor 1. Thinking I had a bad O2 sensor, I returned it and installed new one. Drove to get gas this morning, car running fine, and on the way home---Service Engine Light back on, code P0133---slow response Bank 1 Sensor 1. No exhaust leaks, no coolant leaks, wires not touching exhaust. I have no idea. Any help would be appreciated. Short scan is attached after filling tank and SEL light came on.

[Jay@HAP]

Why did you replace the 02 sensor to begin with?
what brand of sensor did you replace it with?
Is the P0133 code new since the new sensor has been installed?

[Russ K]

Slow response codes are common when headers are installed. Just set that code to no error reported.

Russ Kemp

[5FDP]

Yup, P1133 means nothing and doesn't matter really as it's a very common issue with headers on a 3800.

[coachcrow56]

I replaced the sensor because it had almost 50,000 miles on it---I know they last longer---but I replaced it with an identical DENSO. It has never had an SEL before and I have had headers on the car for over 10 years.

[and]

I replaced the sensor because it had almost 50,000 miles on it---I know they last longer---but I replaced it with an identical DENSO. It has never had an SEL before and I have had headers on the car for over 10 years.

Simply put the old one back and see if code returns. that will shed some light here.

BTW, this code is often caused by vacuum / pressure leak. If the car idles a bit too high or the fuel trims are high on idle check intake / charger gaskets, PCV, etc.

[coachcrow56]

IAC will act up on occasion and give high idle----shut off car and restart---goes away

[and]

spray carb or brake cleaner around intake, see if fuel trims go down, pinpoint vacuum leak (if any) that way.

[coachcrow56]

No vacuum leaks---no exhaust leaks---no coolant leaks===still a mystery

[and]

swap O2 sensors, you have 2 banks, swap them see if the code follows.

[5FDP]

Not a 3800, it only uses 1 o2 sensor for both banks. The secondary o2 sensor after the cat is only there for emissions purposes.

I had this same issue on new denso sensors back when I owned a grand prix with headers. It made no difference in how the vehicle runs. I remember talking with a guy years back about o2 sensor design, if you compared an old style delco sensor from the late 90's early 2000's you'd see how differently the exhaust gases flowed into the sensor. The new sensor design is much more sensitive and to him and me was a leading cause for why the code is popular with new sensors. Also the placement on the o2 sensor in the downpipe changes the exhaust pulses past the sensor too and makes it act different.

[Fastcp]

Had this same problem replaced factory sensor because of mileage the on freeway going home this code comes up, reset and drove. Next day again on freeway code came back. Replaced sensor with a new Denso, (first installed AcDelco), next day code came back again on freeway. Research found happens a lot with header cars which puts sensor down stream further, only comes on when driving freeway. So these are a heated 02. Now very unhappy no code new parts have code. So I removed sensor and cleaned all the anti seize off sensor and manifold bung reinstalled sensor and no more codes. Afterwards thinking if left untouched eventually code would stay off after so many heat and cool cycles. Again this is what worked for me.