O2 Fault Codes

[KRZ BMW Owner]

My 2000 528 ITa - Motorsport Edition

My wife called me distressed because the car would not idle when she stopped or slowed down. Of course she was trying to take our son to school and was in stop and go traffic.

Originally it registered the following codes:

CA Oxy sensor control limit, cyl #4-6
CB Oxy sensor control limit, cyl #1-3
E3 Oxy sensor adaption limit, Cyl #1-3
E4 Oxy sensor adaption limit, Cyl #4-6
ee Misfire detected, Cyl #1
EF Misfire detected, Cyl #2
F0 Misfire detected, Cyl #3
F1 Misfire detected, Cyl #4
F2 Misfire detected, Cyl #5
F3 Misfire detected, Cyl #6

I did a visual inspection and found that the oil seperator line (part no. 11 15 7 532 649) was severed in half, so i figured that was causing a vacuum leak.

I replaced the oil seperator line, O-ring in the dip stick tube, and since I had it apart went ahead and replaced the rubber bellow/boot between the throttle body and the Mass Air Flow Sensor.

I cleared the fault codes. After about 20 minutes the following fault codes appeared and it would still not idle and ran a little rough:

CA Oxy sensor control limit, cyl #4-6
CB Oxy sensor control limit, cyl #1-3
E3 Oxy sensor adaption limit, Cyl #1-3
E4 Oxy sensor adaption limit, Cyl #4-6
ee Misfire detected, Cyl #1
F0 Misfire detected, Cyl #3
F2 Misfire detected, Cyl #5
F3 Misfire detected, Cyl #6
97 PreCat oxy sensor short to ground, Cyl #1-3
9A PreCat oxy sensor short to ground, Cyl #4-6

That did not take care of it, so I purchased a new Mass Air Flow Sensor (found a Siemens VDO for $190). Drove it around the block and everything seemed fine - it idled and it did not run rough. I brought it back pulled into the garage left it idling then the MIL came on again. It is now registering the following fault codes:

97 PreCat oxy sensor short to ground, Cyl #1-3
9A PreCat oxy sensor short to ground, Cyl #4-6
E3 Oxy sensor adaption limit, Cyl #1-3
E4 Oxy sensor adaption limit, Cyl #4-6
ee Misfire detected, Cyl #1
EF Misfire detected, Cyl #2
F0 Misfire detected, Cyl #3
F1 Misfire detected, Cyl #4
F2 Misfire detected, Cyl #5
F3 Misfire detected, Cyl #6

Luckily I have only thrown $250 worth of parts at it, and it has 110K so I do not feel bad. Did I do something to cause the short to ground fault codes?
Could it be the Idle Control Valve? I tested the throttle position sensor and it is operating correctly.
What about the fuel pump, filter or etc? I did notice that when I filled up the tank of gas, the instrument/gauge in the dashboard indicates half-full despite it being completely full

[rallen133]

did you ever find an answer to your problem.. i'm having the same exact fault codes

[darkhorse737]

pull out 1 or 2 plugs and describe the color of burn... Brown, black, gray or white???

describe plug as well. wet or dry?

for 02 sensor probs. check all fuses ans see all are in order.