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Old 03-16-2011, 07:35 PM   #1
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P2096 and P2098 code help

04 330i zhp with 103K miles. I've had the two codes show up on and off for over a year and would like to resolve it now. Codes are P2096 and P2098 both for "Post catalyst fuel trim system too lean". The CEL goes on, stays on for a couple of weeks then goes off, stays off for a couple of weeks etc. If you clear the CEL the codes show up as pending very quick and then CEL goes on a couple of weeks later. PO installed ebay headers and the o2 sim.

My biggest question is - is it definitely the headers that are causing these codes despite the o2 sim or is it something else? I have researched this a lot and still don't have a plan of attack. Should I change the post-cat o2 sensor? Install the defouler between the o2 sensor and the pipe? Bad o2 sim or wiring? But would headers even cause the too lean condition?
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Old 03-16-2011, 07:50 PM   #2
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you might check the lower intake boot or ccv for vacuum leaks...or it may well be the sims
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Old 03-16-2011, 07:55 PM   #3
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Could be a faulty MAF sensor.
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Old 03-16-2011, 09:09 PM   #4
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Quote:
Originally Posted by 330ciandr6 View Post
you might check the lower intake boot or ccv for vacuum leaks...or it may well be the sims
This was checked - no apparent leaks after spraying carb cleaner all over the intake.

MAF sensor has been cleaned several times as well.
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Old 03-16-2011, 10:03 PM   #5
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Usually LEAN LEAN LEAN means AIR LEAK
Intake vacuum leak throws 0170/0173 (for m54 0171/0174), and you said boots are fine, so I presume you have some air leak somewhere in exhaust system.

OR, your o2sim is not doing its job properly. When o2 sensor fails, computer cannot read the air/fuel ratio anymore, so it could throw codes. Lean, rich, whatever.
I'd read OBD2 o2 sensor data, see if car gets proper data from o2sim. If so, I'd check gaskets go to exhaust system. If not, o2sim would be your prime suspect.
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Old 03-21-2011, 08:17 PM   #6
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Quote:
Originally Posted by mack89 View Post
Usually LEAN LEAN LEAN means AIR LEAK
Intake vacuum leak throws 0170/0173 (for m54 0171/0174), and you said boots are fine, so I presume you have some air leak somewhere in exhaust system.

OR, your o2sim is not doing its job properly. When o2 sensor fails, computer cannot read the air/fuel ratio anymore, so it could throw codes. Lean, rich, whatever.
I'd read OBD2 o2 sensor data, see if car gets proper data from o2sim. If so, I'd check gaskets go to exhaust system. If not, o2sim would be your prime suspect.
Here is the data that I just pulled from the O2 sensors using a computer hooked up with the OBD cable and looking at the live data stream. Sensors below were the only ones reporting. All other showed a static N/A.

*******

02 sensor 2, bank 1: reading between 0.300 to 0.565 volts jumping around every second or so. Most of the time goes from 0.310 or so one second to 0.455or so the other second.

02 sensor 2, bank 2: very similar numbers to above.

*******

02 sensor 1, bank 1 (WR): - 0.020 to 0.219 mA. Eq. ratio jumping around 0.956

02 sensor 1, bank 2 (WR): very similar numbers to above.

*******

Can someone help to interpret the numbers and how it relates to the problem with the CEL that I am having?
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