Code 29F1 DME: Fuel Pressure, Plausibility

martymil

Major General
Sep 6, 2017
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did it happen in the log where it drops rpm from 2500 to 1700 rpm or when you lifted off and the pressure jumped from 72 psi to 90 psi ?
 

Brakthru

Private
Feb 20, 2019
41
2
0
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BMW 335i
This error mostly happens because of unstable and highly fluctuating fuel pressure swings.

Get those swings under control and I highly doubt you will see those errors again.

Next time manually log your car and look at what time the error occurred in history and look at your log and go from there.
They might be related to the faults but I get the faults before getting to 40mph part throttle. Uim not getting the error at all since I adjusted vcv tables. Unfortunately I don't know what's causing the polygraph on hpfp. It seems like traction plays a role with spinning wheels. Maybe the ecu having trouble keep values stable.

On this latest map, I don't see the polygraph or faults. But the notorious dip hpfp around 4k concerns me. 1400-1700 psi then recovers instantly. Tuning vcv is tedious and I still don't have it figured out yet though its better.

My tuner shared the vcv tables he used in my map but it caused the faults so it works for the map he made but not the one I made. His map is for e45 mine is e50.
 

doublespaces

Administrator
Oct 18, 2016
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did it happen in the log where it drops rpm from 2500 to 1700 rpm or when you lifted off and the pressure jumped from 72 psi to 90 psi ?

I think you need to look at the log closer. Rail pressure drops to 189 and lpfp goes into fail safe mode without any change to the accelerator/lifting.
 

doublespaces

Administrator
Oct 18, 2016
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Your tripping a torque limiter for some reason, shouldn't do that at low throttle.

Could be something up with your tune.

The thing is, once I shut down, clear the code and start back up, it doesn't happen again no matter how long I drive. I would avoid the freeway in the morning until it triggered, otherwise I'd be stuck on the on ramps with a stalled car while I try to clear the codes.

So what is the relationship between this torque limiter and the warmup of the vehicle? It wouldn't occur until the next morning once the car had cooled down. Additionally, it only seemed to happen in the winter months when we get cooler weather in AZ.
 

martymil

Major General
Sep 6, 2017
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Thats whats causing your code because the pump goes from 72 to 90psi.

It could be a table thats not quite right in your tune thats causing the torque limiter causing your fuel pressure to spike and causing the error.
 

martymil

Major General
Sep 6, 2017
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try warming up your car to full oil temp or at least half from cold before driving off next time and see if the error persists.
 

doublespaces

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Oct 18, 2016
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Thats whats causing your code because the pump goes from 72 to 90psi.

It could be a table thats not quite right in your tune thats causing the torque limiter causing your fuel pressure to spike and causing the error.

That isn't a fuel pressure spike when it goes to 90. That is the fuel pump running at 100% duty because the car is limping.
 

martymil

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Sep 6, 2017
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I understand but thats because the of the fuel going from 72 to 90 psi instantly is what's tripping the error.

if you had an external fuel pressure reg and set manually to 75psi with a return line that error would not occur most likely
because the fpr would not allow this to happen.
 

Grunt

Private
Jul 30, 2019
28
6
0
Lancaster, P
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2011 335is
Just had the 29F1 code after trying to do a 2 minute update flash to adjust the limit on boost in 1st and 2nd gear. The engine would go into limp mode and the fan would start running at 100% like described earlier in this post. Then the windshield wipers started. ???????? I picked up the updated sensor and line at the local dealership and it seems to have fixed the problem. After replacing, the car started and ran great for 5 minutes and then it happened again. Reflashed again then with the new sensor and it's been running fine now for the last hour.
 

BEASTN54

New Member
Dec 29, 2021
2
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0
You ever figure this out? I get the same thing. I have a new Helix, hpfp, stage 2 bucketless low pressure fuel pump lpf sensor, high pressure fuel sensor. Still on original ekpm2. I have 2 maps. 1 map it doesn't happen. The other map it happens. I know I need 2 rear o2s because I keep getting a faults for o2 after cat signal.
Have the same code 29f1 after almost changing everything rear 02 sensor bank 2 solved the problem. it became so bad that it would go into limp mode every 3 to 400 meter. and hpfp is now pumping.
 

PupkinRacing

Specialist
Aug 31, 2017
79
21
0
Madison, Wisconsin
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Bmw 135i
Any update to this? I just had my car go into limp mode while driving. Got code 29f1 and lost rail pressure exactly as described. Lpfp went up to 90+ psi. Turned car off and waited a few minutes then turned it back on and it ran fine. Nervous to take it anywhere now. Happened after about 20min of highway driving. Have a PFS pod, 19t’s all the supporting mods been running same mods and tune for 30k miles so that’s not the issue. Iam wondering if my stock FPR might be failing? Car has high mileage.