Oxygen Sensor

Hey!
can some one help on the below!
if i have some issue with the oxygen sensor and it is not working properly should the check engine sign on the dashboard be on or no.
thanks in advance

The pre-cat sensors monitor fuel mixture. If the sensor is defective, there will be a Check Engine light on, and a code stored.

appreciate the fast reply
i placed my car (528i/1998) on the scanner and it showed that i have an error (don't remember the code number) in the oxygen sensor, but the check engine light is NOT on.
i tried the test 02 to see if the light is working and it is,
what could be the problem in this case
my brain is so confused now

Can't help without a P-code.

hmm
the code number is 76, will it help ?
keep in mind that i am a Rookie

in Normal BMW 528i/1998 what is the fuel consumption ?
mine is doing 130KM/20Liter of Gazoline
is it good or it is consuming lots of fuel

Your fuel consumption is out of whack.
You might also pull false air (vacuum leak) somwhere.
Check all the rubber lines first The big rubber boot at the "Y" will develop cracks after so many years. The small rubber lines will "feel" OK, but if you attempt to pull on them they either will crumble, or will elongate like chewing gum. There are a couple of rubber plugs as well that start cracking. The DISA will have the O-ring pulling air around the seal.
Then, if the O2 sensors have 100,000 Km under the belt, they start getting lazy and will fail eventually.
The MAF, you can attempt cleaning it, but be careful. Also, in time it will loose the ability to meter correctly the air.
There are 2 more things to check: The ICV - usually it gets carbon buildup and you want to clean it. the internal flapper should move freely (mine was clogged solid, no movement, after 160,000 Km). The TB starts getting oil deposits (sludge) - it will look like a laquer on both sides of the flap.
Old sparkplugs are no help either.
Not sure if the injectors were cleaned, and if the fuel filter was changed. I hope the air filter was changed regularly and looks OK.

These are things that should help improve your fuel economy and make the car run better.

You should get between 11 - 12.5 l/100km city driving and around 7.8 - 8 l/100Km on the hiway.

Originally Posted by H2O

hmm
the code number is 76, will it help ?
keep in mind that i am a Rookie

The BMW numeric fault codes can vary by specific DME (ECU). However a search of a large selection of DMEs found this only

P0150 | 76 | O2 Sensor Circuit (Bank 2 Sensor 1)

Since it references a generic DTC, i.e. P0150, and not a P1xxx OEM specific code, the above is almost certainly correct for your car.
Bank 2 means the rear cylinders 4 through 6. Sensor 1 means pre-cat

You might try simply unplugging and then reconnecting the plug on the side of the valve cover in the hope it's just a bad connection on one of the pins. This is a long shot though.

Replacing I6 pre-cat O2 sensors is an easy DIY although you will need a special socket to do it properly. The socket is not expensive ~ $15 to $25. Check best links for DIY procedure, brands to buy, best prices, etc. for sensors.
EDIT: also a torque wrench to do it right.

Also, it's best to replace O2 sensors in pairs, but not absolutely necessary. Many people report better power and fuel economy after replacing the sensors.

When i replaced my pre O2 sensors i didnt see any difference in fuel economy
Recently i took 300 miles trip and my fuel consumption was crazy 31 !! MPH doing 75 MPH
In the end i tried some spirited driving with 95+ MPH but even then it failed to 28 MPH only
These new O2 sensors did a good job for me
LOL

There is nothing wrong with your car......leave it alone. Your car has a very sophisticated diagnostic system. The Check Engine Light will come on when there is a problem. If you disconnect the O2 sensor and run the engine you WILL turn on the CEL. Leave your car alone.

Originally Posted by H2O

.......... but the check engine light is NOT on.......

Originally Posted by pshovest

There is nothing wrong with your car......leave it alone. Your car has a very sophisticated diagnostic system. The Check Engine Light will come on when there is a problem. If you disconnect the O2 sensor and run the engine you WILL turn on the CEL. Leave your car alone.

His fuel consumption 15 mpg. Something is wrong.

Originally Posted by doru

His fuel consumption 15 mpg. Something is wrong.

I second that. Have you tried cleaning the Mass Airflow Sensor (MAF) with some CRC Sensor cleaner? This could also affect your MPG.

Many thanks for your help, really appreciate it.

Originally Posted by rdl

The BMW numeric fault codes can vary by specific DME (ECU). However a search of a large selection of DMEs found this only

P0150 | 76 | O2 Sensor Circuit (Bank 2 Sensor 1)

Since it references a generic DTC, i.e. P0150, and not a P1xxx OEM specific code, the above is almost certainly correct for your car.
Bank 2 means the rear cylinders 4 through 6. Sensor 1 means pre-cat

You might try simply unplugging and then reconnecting the plug on the side of the valve cover in the hope it's just a bad connection on one of the pins. This is a long shot though.

Replacing I6 pre-cat O2 sensors is an easy DIY although you will need a special socket to do it properly. The socket is not expensive ~ $15 to $25. Check best links for DIY procedure, brands to buy, best prices, etc. for sensors.
EDIT: also a torque wrench to do it right.

Also, it's best to replace O2 sensors in pairs, but not absolutely necessary. Many people report better power and fuel economy after replacing the sensors.

Many thanks for your help

I agree his fuel consumption is much worse then mine, but poor gas mileage doesn't mean there is a mechanical problem. We know nothing about OP's driving conditions in Lebanon. Is OP using OBC MPG reading or is this a manual calc? Has he had car for 2 weeks and PO never reset the OBC MPG? An MPG calc based on 20l (~5 gal) of fuel is inherently inaccurate. Is it based on a fillup or based on fuel gage moving from 60 to 40 liters? 15 MPG is not out of the question in city driving, w/AC on and a heavy foot. With no CEL, 15 MPG is far more likely to be a bad calc or related to driving conditions.

Originally Posted by doru

His fuel consumption 15 mpg. Something is wrong.