Stephen Max

I replaced the precat O2 sensors on my 545i over the weekend, now I'm getting codes for system too lean at idle. I'm positive I got them in good and tight. If the old sensors had lost some of their ability to detect oxygen, then the adaptations would be on the lean side. Now the new sensors are detecting the lean condition and the adaptations need to be reset.

Does this sound logical?

Rizbel

Hi Stephen,
I'm about to replace my precat O2 sensors; I did the postcat O2 sensors last month and got delayed installing the 2 precat O2 sensors due to receiving the wrong part for the right (gray) precat sensor. Do I need to remove the reinforcement plate to access the connector housing to plug in the cables? Any tip is greatly appreciated. Thanks.

Stephen Max

Yes, you do.

After removing the reinforcement plate, disconnect the O2 sensor harnesses at the connector housing. To get at the driver's side O2 sensor, remove the plastic side panel in the wheel well. Then remove the pinch bolt that holds the steering tube to the splined shaft and move the tube out of the way. Now you can get at the O2 sensor. Use a 22 mm open end wrench to remove the sensor. I found it easier to unscrew the sensor if I pulled the harness up and over the exhaust pipe so that it hung down out the access port. That way it could turn freely without twisting up and resisting unscrewing the sensor. Installation is reverse of removal.

The passenger side sensor was a bit more difficult. After you pull the side panel off, you will see steel hydraulic lines crossing the access port if you have the dynamic sway bar option. If you don't, then access is easy. If you do, you will have to squeeze your hands past the hydraulic lines to get at the sensor to unscrew it after loosening it. I was just barely able to do it, and my hands are not large.

Also, the answer to my question above is that I had to reset the lean at idle code a couple of times, but eventually it sorted itself out and I'm not getting the CEL anymore.

f1peterc

I replaced the O2 pre-cat sensors on my SMG 545i without removing the reinforcement plate. Just the plastic covers

Shankar Gopalamurthy

Why are you replacing the o2 sensors?

I have a 530I 2007 version with 125000 kms on it. I have similar issue with dead spot at low rpms. Car does not stop or stall. It just hesitates for a moment and then kicks off to normal speed. I can replicate this in Parking and Neutral mode too. When you accelerate, it struggles a bit and then goes to normal.

Changed everything I could.

Oil Separator
MAF sensor
hose pipes
non return valves
new coils
new plugs
new radiator fan (old one had an issue)
New fuel pump
New fuel filter
Engine oil and filter changed
Transmission valve body changed with new solenoids
Convertor reconditioned
Transmission oil changed to ZF

Cleaned the vanos, DISA, throttle body too. All looks fine.

Did a throttle learning and adaptation reset, quite a few times. Whenever I do it, the car runs fine for 200 to 300 kms and the problem comes back. I take it again to the mechanic to do the reset and the problem goes away for some distance and back again. What do I have to change?

Disa Valve - intake and outlet (there are 2)
Cam shaft sensor
Actuator Motor
Vacuum pump
Throttle body with sensor
Vanos - 2 no's

These are the only things in the engine area that might need a change.

Please advise.

Thank you.

Arjun

seanjordan20

Crankcase vent valve and vent hoses. If you have not changed you disa before do that also. Your issue will be resolved with that