I have a 2000 BMW 540i and I need new O2 sensors. How many do I need and what types. I have read online that there are upstream and downstream sensors. I would also like to know where they are located and how I can install them
"Up-stream" means before the catalytic converters and are probably in the header pipe(s). The "down-stream" O2 sensors are behind the cats in the exhaust system, usually just behind them. Not the expert here on this particular car but there are probably 4 of these sensors. BMW exhaust systems are very tight on space, be careful tackling this job.
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Check which side of your engine has cylinder #1. That side is bank 1. Bank 2 is the side opposite of bank 1. So bank 2 is not always passenger side. And since you seem to have extra O2 sensors, I would replace the other upstream and see what happens. Also the mass air sensor can give a trouble code issue to the upstream 02 sensors. Good luck. I've struggled thru this myself.
The code P0137 means that your downstream O2 sensor has low volts. A rich running engine makes the voltage go high, not low. If the upstream sensor is not reading a rich or lean condition, then you need to replace your downstream O2 sensor.
P0430....Catalyst System Efficiency Below Threshold (Bank 2)try changing the O2 sensors the one before the cat is the first one to fail in normal circumstances ,must be an american market model this vehicle as i cannot read a europeon market vehcle here in europe ,encrypted software
did u change the right o2 sensor there is 2 sensors on bank1 and 2 on bank2.....upstream and down stream.....i had the same prob i changed the o2 senser to the other side to check and make sure it was the o2 senser....it took 4 o2 sensors before i got 1 that finally worked nd yes i was buying them brand new.....so change sides with it nd see if the code changes sides....and did u reset it with the code machine when u put the new 1 in?
if the 02 sensor is unplugged and you are reading a scan tool from the diagnostic link then of course the 02 reading is wrong
if you are using a volt meter right at the connector thats on the sensor then the 02 will read lean because the heating elements in it are disconnected when you unplug it
check 02 voltage with engine warmed up and 02 sensor connected you will have to pierce insulation with your probe
Your auto has four O2 sensors. Two upstream and two downstream; With two banks. Bank 1, sensor 1...and bank 2, sensor 1 are the two upstream (exhaust manifold before the catalytic). Bank 1, sensor 2 and bank 2, sensor 2 (other side of catalytic)
Code 1131= upstream; bank 1..sensor 1 Code 1151= upstream; bank 2..sensor 1 Code P0136 (generic code) bank 1..sensor 2 (questionable)
I wouldn't spend the money to purchase 3 sensors. Highly unlikely all three are bad; Cost is about $40/ ea. Since there isn't a code for the cat's themselves, I would suspect the O2 circuit is malfunctioning. The rough idle is another clue.
Take an ohmmeter set it on X10 scale and measure the resistance from engine to body and body to negative post on battery terminal. You should read zero ohms (full needle deflection). If you do go buy two upstream O2 sensors. If you read open or a high resistance run two straps from eng. to body...and body to neg.batt. post.
Downstream O2 sensor is after (downstream) the catalitic converter on the exhaust pipe. Upstream O2 sensor is after (downstream) the engine exhaust manifold - before (upstream) the catalitic converter. Upstream O2 sensor controls air-to-fuel ratio to yield a small excess oxygen. Downstream O2 sensor assesses the catalitic converter performance.