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Fuel pressure code, 29F3: DME: fuel low-pressure sensor, electric

Tiny
DIVIDES
  • MEMBER
  • 2008 BMW 535I
  • 6 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 208,000 MILES
The car idles rough first thing when you start it. The car drives great, had several codes which I am sure were triggered by one, as is the case with BMWs. Cleared all and only one that came back after 6 miles of driving is
29F3: DME: fuel low-pressure sensor, electric.
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Friday, April 1st, 2022 AT 11:28 AM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

The code likely indicates a poor connection. The sensor could be bad, but according to the diagnostics, it indicates checking wiring and connectors first. (Pic 1 below)

To access the low-pressure sensor, the throttle body needs to be removed. Once removed, you will have access. See pic 2 for location.

If the connector and wiring are in good condition, check for a 5v reference in the plug.

Let me know what you find.

Joe

See pics below.
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Friday, April 1st, 2022 AT 10:06 PM
Tiny
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  • 898 POSTS
Got some readings from scanner, but this low-pressure reading does not change, whether car is off or on, while the high-pressure readings move.
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Tuesday, April 5th, 2022 AT 12:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I suspect you have an issue with the low-pressure sensor. Were you able to perform the tests listed above?

Let me know.

Joe
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Tuesday, April 5th, 2022 AT 6:36 PM
Tiny
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Checked connector and it looks good. Ground is there and 5v is there.
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Monday, April 18th, 2022 AT 9:47 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

If everything is present (power/ground) and in good condition, it sounds like the sensor itself is bad. Have you tried replacing it?

Let me know.

Joe
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Monday, April 18th, 2022 AT 2:39 PM
Tiny
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Ordered one, will keep you updated. So, this sensor monitors the low-pressure side? What is its function?
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Monday, April 18th, 2022 AT 2:45 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

Basically, it monitors pressure and signals the PCM if there are variations. The PCM in turn uses the information to control injection timing and to maintain the highest level of performance.

Let me know if that takes care of the issue.

Take care,

Joe
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Monday, April 18th, 2022 AT 8:46 PM
Tiny
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The new sensor has taken care of the issue. Thanks to your help.
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Monday, April 25th, 2022 AT 3:36 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

You are very welcome and thanks for letting me know. I'm glad to hear it is running well again.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe
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Monday, April 25th, 2022 AT 6:30 PM

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