No, I usually fully diagnose and investigate faults very thoroughly, however, I have been working on vehicles for a LONG time and I have found that there are some things that are not worth screwing around with.

Unlike a weak battery that can leave you stranded, a weak battery can be jump started and in some cases the car can be roll started. Additionally weak batteries do not typically cause problems while driving, they can, but RARELY do.

When a fuel pump starts to have problems it can leave you in a bad situation on the road or in traffic and not IF, but WHEN it fails it will generally leave you stranded where you are. No jump starting, roll starting or other things other than a tow will get you going again.

There are some subsystems that are not worth screwing around with.

Many, many BMW models have a very clear history of fuel pumps that both hard fail and soft fail. Fuel pump life has very little to do with actual mileage, it has to do with run hours. A highway queen may have far more miles and far fewer run hours then a city queen that spends its time in stop and go traffic and idling at traffic lights. It seems that approximately 5000 hours is about the expected lifespan of many fuel pumps.

I find that after about 8 years you are on borrowed time.

When I bought my E70 X5 with 66k miles on it, I quickly replaced the fuel pump as PM replacement. The fuel filter is integrated into the fuel pump and I know all too well about the E46, E39, E38 series fuel pumps. I had a number of 1100 mile trips I was going to be making once I purchased the X5 and made a conscience decision to replace the fuel pump on MY schedule, not on the CARS schedule.

It was not worth the risk of me being stranded and the headache and inconvenience.

I had a spare fuel pump for my E46 on the shelf for 2 1/2 years before I replaced it. The E46 is a city dweller and is never far from home. I had planned on replacing it on the cars 8th birthday, but the weather got the best of me and I missed my mark by about 2 weeks. Temps dropped to below 20F and one morning I went out to start the car and the FPR was moaning, I knew the pump was on very borrowed time. Drove the car that day, then next morning, no start. Did I diagnose anything, no, I knew the car needed a fuel pump, I had the fuel pump, I had planned on installing the fuel pump and did not get to it.

So rather that even opening the hood, I went out, pulled the rear seat and replaced the fuel pump in 14 minutes. Yea, the colder it gets, the faster I work.

Now I am glad I replaced the pump proactively on my E70. BMW has extended the Warranty on the E70 fuel pumps, they know they have issues. Additionally, the E70 fuel pump replacement is not a 14 minute swap! I would not have been very happy replacing the pump on the side of the road or in below freezing weather.

Again, do what you what, others will do what they want, but based on my driving style and schedule as knowing it is not IF, but WHEN the pump will go soft or just hard fail, I replace fuel pumps by the cars 8th birthday.

Thanks for all the inputs. I really appreciate it. Yesterday I cleared the codes and see if it comes back today. Meanwhile, the fuel gauge is arriving Friday so I will report back once I have the fuel pressure date.

As for the fuel trim data, I'm a little too green to figure out how to do that. Any suggestion will be appreciated.

Thanks again!


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Hopefully the fuel pressure gauge you are getting has a bleeder port to measure fuel volume as well? Not many have this feature.

As for Fuel Trim values, need to know what OBDII tool you are using.

And for all the naysayers out there that claim there is nothing to be concerned about the OP's fuel pump, I mean come on, the pump is likely the original and at least 14 years old, how many years to you expect it to last beyond 14 years and its is amazing it is still working at this point. Also keep in mind MILEAGE has very little to do with an electric fuel lifespan, it is all an hours based wear issue. Keep in mind for every second the engine is running, the fuel pump is also running, even while you are stopped at a traffic light and the vehicle mileage is not moving the pump continues to run and the brushes continue to wear.

The Pierburg pumps seem to last a bit longer than the Siemens/VDO pumps, not exactly sure why, but this vehicle likely still has the original fuel pump installed. 5 minutes to pull the rear seat and check for to see if the sound proofing has been cut or disturbed will give you and idea as to what is going on with the vehicle if the past history is unknown.

It does not matter why the O2 sensors were replaced, often when they are replaced, fresh O2 sensors are more active and sensitive and will trigger other codes that older, lazy O2 sensors may miss.

Additionally, with the EXCEPTION of a failed heater circuit, I never see any O2 sensor related codes that are actually for a failed or lazy O2 sensor. Almost any code that references an O2 sensor, with the exception of a failed heater circuit, tend not to be anything to do with O2 sensors.

This is the problem with people that do not think and even the industry Pros, if a sensor is mentioned in a DTC, they automatically condemn the sensor. WRONG, WRONG, WRONG way of doing business.

Addition, there is no O2 sensors testing software that works that I have found, nothing what so ever. I use a $4 App and Log the O2 sensor from cold start. I can find bad O2 sensors all day long that never trigger any O2 sensor codes and that never trigger any DTC's. Any yes, I have more money wrapped up on Pro level tools and software than you have in your vehicle and I still use my $4 App all day long to flag and condemn bad sensors that pass every where else.

The OP does not need to do anything with his current O2 sensors other than to verify the wiring is not swapped Bank to Bank.

I will post an example of some O2 sensors that never had any errors, BUT, they were causing the SAP Readiness Monitor to no turn to Ready/Clear/Pass. I just need to access the files.

Problem here is there are codes without symptoms.

Always start with troubleshooting, even when the problem seems obvious, in particular stuff that doesn't cost much and easy to do that will narrow it down to the root cause.

Since the codes are primarily limited to bank one I would first check the wire connections on the O2 sensors on that bank. If they are fine you could swap the sensors side to side to see if code moves to Bank 2. Not sure how you can have them connected to the wrong bank because of the distance they are apart from one another. Pre cat O2 sensors are primarily dedicated to fuel trim. Post cat are primarily dedicated to emissions but depending on the engine it can also influence fuel trim a bit. I would check plug holes on bank 1 for oil and if none pull those plugs and see how they look. You could also have an injector that is plugged on that bank (could start with filling up with gas that has Techron in it and adding a bottle to the tank). It could also be a coil on that bank.

Beyond that, fill the tank, clear the codes and see if they return before a 1/4 tank. Check for vacuum leaks--smoke test is best but spraying carb cleaner around typical vacuum leak areas will sometimes find a leak (engine will increase rpms). Common place for vacuum leak is the air intake tube near the throttle body. Clean the MAF with MAF cleaner. You could have rented--with full refund of rental cost when it is returned--a fuel pressure tool at major auto parts stores. Check the air filter, mostly for grins, but ya never know.

Not twisting any words here, stating what needs to be stated.

Your "testing" of O2 sensors with what ever software you are using is SO wrong it is not even funny. This is just like the Pro techs that look at the O2 sensor Voltage swings and "think" they can determine a good vs a bad sensor, you can't do that under almost ever circumstance.

Here is a VERY clear example of verifying good vs lazy O2 sensors. The cold start behavior is CRITICAL to determine the sensor health. Note this graph is from an E46 and the deep "V" negative Voltage swing is due to the SAP running and pumping extra air into the exhaust stream. You can see how the old sensors do not react like the fresh sensors react.

TOO many people "think" they know how to monitor and test things, there is no software that I have found that will do this automatically because there are no software developers that understand how to accurately and properly flag lazy sensors.

The other reason the OP is likely suffering all the sudden from Lean codes is due the overnight temps dropping into the upper 30F to lower 40F.

Vacuum leaks and weak fuel pump are PRIME reasons for the cold start errors on a 10+ year old BMW I6. This is nothing new.