2003 318, N42B20 fault codes

[Coolmom]

Hello,

So I was cruising at about 60mph when my CEL came on, and i caught these codes on ISTA-D:

00271C DME: Oxygen sensor after cat., bank 1 - signal
002738 DME: Catalytic-converter conversion, bank 1
002761 DME: Secondary-air system, bank 2

Now I cleared the error memory and drove around 10 miles, but the CEL has not come on again.

Any thoughts? The car feels like it has some minor power loss, but besides that it's running as usual. I was thinking about replacing the o2 sensors, but might aswell ask for some opinions first

[MarcoZandrini]

The second code is likely caused by the first code. That is, the after catalytic converter oxygen sensor is acting up, thus the DME thinks there’s a problem with the converter. You car has a 4 cylinder engine so there is no bank 2. BMW engines with 6 or more cylinders have 2 banks. For a 6 cylinder engine bank 1 is cylinders 1-3, bank 2 is cylinders 4-6.

[Coolmom]

The second code is likely caused by the first code. That is, the after catalytic converter oxygen sensor is acting up, thus the DME thinks there’s a problem with the converter. You car has a 4 cylinder engine so there is no bank 2. BMW engines with 6 or more cylinders have 2 banks. For a 6 cylinder engine bank 1 is cylinders 1-3, bank 2 is cylinders 4-6.

Thank you for your response. Should I just ignore the code related to bank 2 then?

[dworthy]

On the secondary air system, there is only 1 bank so I find it odd that it shows bank 2, so yeah don't worry about it. What you can do is look for the pump to see if it is turning on. Normally the car has to be cold, and it will run for about 60-90 seconds on start up. Another fail point on that motor is the check valve for the Secondary air system, as it will allow exhaust gases to flow back into the pump and not close all the way.

[Coolmom]

I will check the secondary-air system once the car has cooled down; I did take her for a test drive for around 60km on the highway doing 120-140kmh to warm the catalytic converters up.

After that, no CEL but now the only code i'm getting is still 2738 DME: Catalytic-converter conversion, bank 1
I noticed that the car has a deeper/rumblish tone; could an exhaust leak cause this code to pop up?

[dworthy]

Not that I know of, for the code tends to mean you are out of the proper mixture range for the cat to work properly. I would wonder if old oxygen sensors is causing this, or if you have one newer than the other. Since you do have ISTA, see about watching live data, for typically there is a green zone the oxygen sensors need to stay in, see which one is going outside the green zone.

[Coolmom]

here are my inpa readings.

[dworthy]

Everything looks proper, now take if for a drive and see if it stays in the green zone.