My CEL light came on again. The code was P0133 which I know for the 2002 Volvo s40 is an faulty O2 sensor. I am not sure which one though, I have 2 on this car. Also, the tech wrote B151 on the note he gave me after running the ODB2 test. I am guessing that is the sensor location.


I can replace the sensor easily enough, I am just needing to know which O2 sensor is it and can I get away with a non-Volvo O2 sensor say get one manufactured by Bosch?


Any help appreciated. Thanks in advance.


Respectfully,


Lou Reed

 

P0133 is for the rear O2 sensor reporting that there's too much of a different between the front and rear sensors. Its supposed to measure the performance of the CAT... I get this from time to time on my 850T - which has a newish CAT and Walker brand sensors. I usually just clear the code and it comes back randomly. I think your options are a) clear the code whenever b) check for vacuum leaks to make sure the front O2 sensor isn't working too hard c) check the harness / connections on the rear sensor and if needed replace. You can consider using a Bosch generic (without the wiring harness) that splices in to save some $$. d) if you have done other engine mods consider using a Cel-boss to move the sensor out of the exhaust stream. Many ECU tunes eliminate even reading/comparing the rear sensor...

 

What is a Cel-boss?


Respectfully,


Newport_j

 

https://www.ipdusa.com/products/8656...-sensor-spacer

here's one example from IPD. There's more on oxygen sensor spacers on ebay for under $10. I was also reading a post where their P0133 was being created by a faulty fuel pressure damper. Vacuum line fell off and was creating periodic surges of fuel pressure creating a short term rich burn not noticed during driving or by other fault codes, enough to trigger a P0133 code though... Hmmm.

 

I have a 2001 Volvo S40 with P0133 O2 sensor code for upstream sensor. I replaced both up stream and down stream sensors. Still have code. I checked and fixed potential vacuum leaks, light still on. I am using Bosch sensors. When I took the old ones off, the downstream had an extension or adapter cable, by Volvo, about a foot long. I did not use that with the new sensors. I just now put the extension plug on the upstream sensor, and that fixed the code. So far, so good.

 

Correction, my post above about using the adapter cable did not work. I have the P0133 code again. I am going to look at the fuel pressure regulator next. Frustrating.

 

Use the CEL Boss and forget that stupid code ever again.

 

Can I get some information on what the CEL Boss is? I tried looking it up and just saw a few discussions on it. thanks.

 

What I found was it is some type of extension on the downstream sensor, even though the error code is on the up stream sensor.

 

You are correct, the CEL Boss is for the downstream or after cat sensor. There was no way in hades I was going to buy a new cat and rebuild the turbo just because Volvo decided to put a super sensitive O2 sensor in their emissions scheme. If the car passes smog then so be it.

Now the upper O2 sensor has it's own issues. The original sensor had an issue from the factory where the wiring harness had a couple of wires reversed. Volvo fixed this with a add-on harness between the original car harness and the O2 sensor harness. I believe the latest O2 sensors have been wired to fit the original harness correctly with no need for the add-on harness. The downstream sensor never had the harness so make sure you do not have them reversed.

 

What code would CEL Boss address? I have three and if I can get rid of at least one with a CEL Boss I would. I just need to know what code(s) it eliminates?

Any help appreciated. thanks in advance.

Respectfully,

Newport_j

 

they can be found on Amazon (search for oxygen sensor spacer) or IPD USA