Pre-Cat Oxygen sensor?

[bawareca]

Originally Posted by ard

These days the BMWs do odd stuff with voltage regulation and charging..I believe the voltage is allowed to drop too low after starting but during operation and this can throw off odd errors from some modules. just weird random modules with faults. You wont notice running issues but the stuff hanging on the bus will not be happy.

Just wag.

Absolutely!It is probably just a random code.
As a matter of fact the computer is monitoring the voltage of the battery and the current that is drawn and if the voltage drops too quickly it will throw a code and warning light.It may not come back for a long time.I have had some stored in my car's memory,but the car will start after being parked for 2 weeks.

[ard]

Originally Posted by bawareca

Absolutely!It is probably just a random code.
As a matter of fact the computer is monitoring the voltage of the battery and the current that is drawn and if the voltage drops too quickly it will throw a code and warning light.It may not come back for a long time.I have had some stored in my car's memory,but the car will start after being parked for 2 weeks.

Question:

Will it show the 'workshop service' warning? Like this:



but not a CEL??? (Which is the classic 'yellow engine symbol')

[bawareca]

I am really not sure if accelerated battery discharge will show the "workshop service",but for sure it will not trigger CEL,except there are some major power supply issues.

[lanbrown]

I think it shows a battery in the gauge cluster but the lift in the NAV screen.

[PHL08]

Originally Posted by ard

These would be the ones that set a CEL, actually I think just the first two.

One is an O2 sensor HEATER code, which means the wire to the O2 is disconnected or the fuse is blown or the sensor massively failed.

Check all connections to the O2 sensors- pop them apart and reconnect them.

Second code i2a99 is an exhaust camshaft correlation. Im guessing a camshaft position sensor? The other issue can be a sluggish VANOS solenoid. Usually due to fouling of the solenoid due to BMWs horrific oil change intervals. Pop them out, flush/clean them, replace Orings.... at least on E39s.

Last one I dunno- seems like a battery issue. How old is you battery? Any charging/voltage issues?

Updating the thread...I finally replaced the sensor. It was the pre-cat, bank 2 sensor. Nothing else. Engine light stayed off after the replacement, and none of the prior codes have come back.

But this is not an easy DIY for this model car (2008 E70). It's extremely difficult to get to the pre cat 2nd bank (rear) O2 sensor, and even more difficult to get the wire routed to the plug because it goes around the back of the engine. Looking down at the engine, the sensors are on the left down under the spark plugs. You can see the bank 1 pre-cat sensor fairly easily. The bank 2 sensor is under a shield that has to be removed. The wiring from the probes goes around the rear of the engine to the connectors on the rear right side (looking down at the engine and into the back with a flashlight).

I had the car in an indy shop for front left suspension work and provided the mechanic the probe to install for me. He did it in about an hour, and that was because he had a lift to jack the car up over his head so he could easier get to the wiring. But not after he had to remove most of the components on top of the engine and around the firewall to also get to the probe and connectors.

Probe was about $130. His labor was another $100'ish. Money well spent because I would have been cussing and swearing every second I was trying to do that myself.

[Arby1028]

PHL08 - sent you a pm on this. Where'd you get the oxygen sensor for $130 and do you have the part number? Thanks!!!

[PHL08]

Originally Posted by Arby1028

PHL08 - sent you a pm on this. Where'd you get the oxygen sensor for $130 and do you have the part number? Thanks!!!

Replied privately, but for others needing this same part..

Bosch 11787558081

I got it from a dealer on eBay. But just googling that above term reveals lots of sellers (at higher prices, too).