So I noticed that for the past week my gas mileage decreased significantly and today my check engine light came on.. p0150 p0325 p0136.. o2 sensors and knock sensor.. would 2 bad o2 sensors cause bad gas mileage?

 

No doubt bad upstream O2 sensors will harm the gas mileage. Those sensors control the air/ fuel ratio.

I replaced both my upstream O2 sensors with Bosch 13242 sensors nine years ago and they're still holding today. They're also sold at much lower prices today.

Edit: The knock sensor code could be trailing the O2 sensor code. Replace the O2 sensor first and clear the codes. Wait to see if the knock sensor codes doesn't come back.

 

but what would cause both o2 sensors to go out at the same time? could it be because i installed a catback exhaust? .. is it absolutely necessary to replace the knock sensor?

 

What catback setup did you install? Only a bad CAT or a faulty rear O2 sensor will throw the po136 code. Another possibility is the rear O2 sensor wasn't re-installed properly on the catback bung or it's connector. That rear sensor only measures the CAT efficiency and doesn't control air/ fuel ratio.

The po150 code indicates the O2 sensor on front section of the y-pipe is faulty.

As I mentioned earlier solve those O2 sensor codes first and ignore the knock sensor code for now. When you clear the O2 sensor codes check if the knock sensor code has dropped. That knock sensor is probably fine and just trailing the O2 sensor codes.

 

Are all three sensors the same part number? Is it possible that they are just dirty n need to be cleaned? .. I really appreciate your help bro

 

The two upstream O2 sensors connected to the y-pipe are the same but different from the downstream O2 sensor after the CAT.

Cleaning the O2 sensor will do no harm but won't solve your error. Code po150 is stating that front upstream O2 sensor is gone or it's harness is faulty. The connector for that front O2 sensor is seated between the front valve cover and radiator fans.

That faulty upstream O2 sensor could of damaged the CAT with a rich fuel mixture. Another possibility is the downstream O2 sensor wasn't mounted properly during the catback replacement.

 

If all three are giving codes, check the O2 heater circuit fuse.

 

Where is that located

 

That crossed my mind but when that fuse blew on me I also code p0136 along with his p0135 and p0150 codes?

 

It's to the left of the steering wheel under the dash. It's fuse #31 15amp.

 

Is the Bosch 13242 part number for the pre cat o2 sensors?

 

Yes. Those are the upstream O2 sensors mounted on the y-pipe.

My downstream O2 sensor after the CAT hasn't failed yet so I cannot give recommendations for that one.