Scan Codes...

[3800SERIESII]

Well, I finally brought myself to O'Reilly's today to use their scanner. I went there because ever since I bought this Bonneville in the late summer 2013, the gas mileage has been sketchy. No lines are leaking, it may be a fuel cap seat issue, but the codes that I discovered may be the dominant culprit to the 10 to 14 MPG I have experienced this winter. The 5 codes are below, and two of them are actually the same (dont know why it pulled one up twice). Could this be strictly electrical?

[Datbonneville1]

A new and or good used egr valve, and a new and or good used b1 s1 o2 should get rid of those codes and improve your mileage!

[3800SERIESII]

A new and or good used egr valve, and a new and or good used b1 s1 o2 should get rid of those codes and improve your mileage!

Hoping that wasn't the case but gotta face it at some point. Can get a new EGR valve for $50 online. The bank 1 sensor 2 oxygen sensor code is post-cat right? the one after the cat and not on the rear manifold? Could a bad sensor cause the cat to get hotter than normal?

[Bob Dillon]

Gee, no wonder your mileage sucks-the car's in open loop WITH a gigantic vacuum leak, the stuck EGR valve.

I'd try cleaning the EGR valve first-they get coked up with carbon and stick, and are easy to clean, replace the O2 sensor and that should cure your problems. Spend the extra money for a Delco O2 sensor. It's worth it.

Also, replace the gas cap.

I'm really surprised the car is driveable. Bet it's bucking like a bronco.

[3800SERIESII]

Gee, no wonder your mileage sucks-the car's in open loop WITH a gigantic vacuum leak, the stuck EGR valve.

I'd try cleaning the EGR valve first-they get coked up with carbon and stick, and are easy to clean, replace the O2 sensor and that should cure your problems. Spend the extra money for a Delco O2 sensor. It's worth it.

Also, replace the gas cap.

I'm really surprised the car is driveable. Bet it's bucking like a bronco.

Thank you for the detailed insight. I will go for cleaning the EGR first, but how would I go about doing so and would I need a new gasket?

Also, the car surprisingly runs fairly normal and quiet and idles decent. It may lack a little umph though..

[SSEBonne4evr]

We call this multiple ghost codes, it is most likely a bad connector continuity
at the PCM.
Put the connector on and off of few times clear everything and re-try it.

[3800SERIESII]

We call this multiple ghost codes, it is most likely a bad connector continuity
at the PCM.
Put the connector on and off of few times clear everything and re-try it.

Do you happen to know which connector on the PCM it is?