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Check engine light with fuel trim above permissible limit?

Tiny
JEFF_18
  • MEMBER
  • 2002 BMW 325I
  • 2.5L
  • 6 CYL
  • 2WD
  • MANUAL
  • 147,000 MILES
My friend's vehicle listed above 325ci keeps throwing the check engine light with fuel trim above permissible limit code and many other codes. I have attached pictures of the codes. He changed multiple parts on the car including all the oxygen sensors, fixed all the vacuum leaks, changed the PCV valve and the hoses. When the car is driven on the highway for long periods of time the check engine light will not illuminate. It’s the city driving that does it. I am out of ideas and any help is appreciated.
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Wednesday, April 17th, 2024 AT 4:50 PM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,874 POSTS
Hi,

I can't see the trims in the video. How high are they? Also, since it is both banks, I would be checking fuel pump pressure as well as checking for engine vacuum leaks. If you haven't done that already, start there.

Here are two links. One explains how to check for a vacuum leak and the other is a general description for testing fuel pressure.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I attached the fuel pressure specifications below. It indicates 3.5 bar in the manual. That works out to slightly over 50 psi.

Let me know what you find.,

joe

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Wednesday, April 17th, 2024 AT 6:28 PM
Tiny
JEFF_18
  • MEMBER
  • 16 POSTS
Thanks for the reply. The fuel pump was changed about a year ago. I will try to check the fuel pressure if I can. We corrected all the vacuum leaks that we could find but it still has the issue. We suspect the DISA valve is not operating properly.
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Thursday, April 18th, 2024 AT 12:46 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,874 POSTS
Hi,

It could be related to the change over valve. There is a fuse (3 amp) under the hood that powers things. Make sure it is good and has power to and from it. Also, confirm power is getting where it needs to be.

I attached a basic pic below of the fuse/wiring.

Let me know what you find.

Joe

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Thursday, April 18th, 2024 AT 6:31 PM
Tiny
JEFF_18
  • MEMBER
  • 16 POSTS
I have attached a picture of the fuel trims with this. We checked for vacuum leaks found a major leak right after the mass airflow sensor. We fixed that and took it out for a drive and immediately after driving a few miles, codes were already pending. The codes are P2098 and P2096 again. All oxygen sensors were replaced with OEM brands.
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Saturday, April 27th, 2024 AT 8:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,874 POSTS
Hi,

In a perfect world, you want the trims to be 0%, but that usually doesn't happen. When you scanned, was the engine at operating temp? Also, if you watch the o2 sensor voltages, do they change or are they constantly steady, unchanging?

Let me know.

Joe
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Saturday, April 27th, 2024 AT 9:08 PM
Tiny
JEFF_18
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  • 16 POSTS
The engine was at operating temps and we drove the car 60 miles just now. Oxygen sensor voltages were changing but B2S2 sensor doesn’t move much. It doesn’t go any higher than 0.25 V. The DISA valve was also changed yesterday while tackling vacuum leaks.
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Saturday, April 27th, 2024 AT 9:12 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,874 POSTS
Hi,

If the sensor is operating at 0.25v, is sensor one doing the same? Take a look through this link and let me know if you can check this. The sensor voltage should drop for a split second when you hit the throttle. Check to see if that happens.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Let me know.

Joe
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Sunday, April 28th, 2024 AT 6:48 PM
Tiny
JEFF_18
  • MEMBER
  • 16 POSTS
Sensor 1 fluctuates and has no issues. We swapped the connectors of both sensors and bank 2 sensor 2 which was not fluctuating much before started operating properly as it should but sensor 1 will not fluctuate much. We can’t find any exhaust leaks as well. The fuel pressure was also at 50 PSI at all times.
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Monday, April 29th, 2024 AT 7:23 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,874 POSTS
Hi,

If I understand correctly, when you changed the connectors, the sensor started working properly, correct? And then when the original connector was moved to bank 1, the sensor had a slow response. If that is the case, the connector itself may be the problem or one of the wires (under the insulation) may be damaged and not seen.

Let me know.

Joe
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Monday, April 29th, 2024 AT 7:48 PM

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