o2 sensors

[Booyaazaa]

Hello everyone,

Recently my 535i hit 100k miles on the odo which the last 40k I've been FBO'd and running a E30 map or more recently the last 4 months a E45 map. The car has been trouble free besides the normal BMW repairs and I do a lot of preventative maintenance to keep it happy. In the last month I've been getting 2c31 quickly proceeded by a 2c6b and then a 2c32 will show up. I've noticed too that on my V3 display the AFR's for those banks go wildly crazy when the codes are present. Also these pre cat codes will show up randomly, driving around town or blasting down I5. Im not sure what the lifespan of the sensors are so is it time to replace the pre-cat sensors? Or is there something else going on. Let me know and any help is appreciated. Thanks.

[R.G.]

Check that the turbo to downpipes clamps are snug before jumping on new O2s. It's a pain in the ass but can save you a few shakels if it turns out to be the problem. Full disclosure: don't know code descriptions and too lazy at the moment to look in to it. Post them

[ajm8127]

The 2C6B is a secondary bank 1 O2 "system check" code. The other codes are bank 1 and 2 primary O2 sensor trim codes. I have read the response time of O2 sensors can slow over time.

I don't know what would cause an O2 system check code, but you could do general inspection like looking at the clamps RG recommends above. Check that wiring and connectors are in good shape. You could try swapping sensors around to see how that affects the codes as well. Though I cant remember if the rear sensors' connectors are keyed differently.

Some people say leave the sensors alone until they cause problems and others say replace them at regular intervals. If you are tuned it might be good to look at changing them like preventative maintenance. It's up to you. To do all the sensors it is between $400-500 in parts.

You will need Bosch 17098 and 17099 for the primary sensors, though the 17098 is more common and easier to find (usually means cheaper) and it can be used in both banks as long as you plug them into the correct connectors.

Bosch lists four rear sensors. 16795, 16976, 16413 and 16414. I think the former two are an older design and the later two are the replacements. 16795 and 16796 as listed as "while stocks last" on the boschautoparts.com site.

I would try replacing the rear one(s) first if you decide to replace them.

[duracell8]

Do you have a backend flash?

[Booyaazaa]

Check that the turbo to downpipes clamps are snug before jumping on new O2s. It's a pain in the ass but can save you a few shakels if it turns out to be the problem. Full disclosure: don't know code descriptions and too lazy at the moment to look in to it. Post them

Yeah I check that just to make sure they were tight which they are.
2c31 lambda probe precat 1 trimming control
2c6b lambda sensor post cat 1 monitor (figured would trigger if a 2c31 is triggered)
2c32 lambda probe precat 2 trimming control

The 2C6B is a secondary bank 1 O2 "system check" code. The other codes are bank 1 and 2 primary O2 sensor trim codes. I have read the response time of O2 sensors can slow over time.

I don't know what would cause an O2 system check code, but you could do general inspection like looking at the clamps RG recommends above. Check that wiring and connectors are in good shape. You could try swapping sensors around to see how that affects the codes as well. Though I cant remember if the rear sensors' connectors are keyed differently.

Some people say leave the sensors alone until they cause problems and others say replace them at regular intervals. If you are tuned it might be good to look at changing them like preventative maintenance. It's up to you. To do all the sensors it is between $400-500 in parts.

You will need Bosch 17098 and 17099 for the primary sensors, though the 17098 is more common and easier to find (usually means cheaper) and it can be used in both banks as long as you plug them into the correct connectors.

Bosch lists four rear sensors. 16795, 16976, 16413 and 16414. I think the former two are an older design and the later two are the replacements. 16795 and 16796 as listed as "while stocks last" on the boschautoparts.com site.

I would try replacing the rear one(s) first if you decide to replace them.

Cool thanks for the info. I've heard the same that they usually last around 125k-150k miles in a regular use application.

Do you have a backend flash?

Im running a custom Cobb tune. A few guys, who are way smarter then me at using ATR, helped me make a E45 map that I've been running for the last 4 months.