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Discussion Starter #1
Ok, so I purchased a mint condition 06 back in September of last year with 69K on the clock. I’ve put about 12K miles on it since then and so far no problems besides regular maintenance and I replaced the front thrust control arms myself which cost me about $300.

So far so good, except I down-shifted to 3rd and took it up to about 7K RPM about 2 weeks ago and I got a CEL and “Engine Malfunction, Reduced Power” message. I hooked it up to BMW DIS/GT1 and it told me “DME – 2788 Fuel pressure, set point/actual value comparison at maximum pressure – Fuel delivery below threshold” or something like that.

If I drive it below 5K RPM the CEL and message goes away.

Researching here on the M5 Forum I found it could be; Fuel Pressure Sensor, Fuel Filter, or Fuel Pump. I’ll probably replace the Fuel Filter anyway but before I start buying and replacing good parts is there any way to narrow it down?

I’m thinking it’s the Fuel Pump because the secondary pump kicks in over 5K RPM and that’s when I get the CEL and message. If I drive 5K and below the CEL and message go away.

Thoughts?
 

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I had this same issue and fault code - it first showed itself at a trackday (Nurburgring). I started out by changing the fuel filter seeing i'd have to do it anyway. When changing it, I was surprised to see how dirty the filter was - the fuel that run out from it was black/gritty!

Since changing it i've not had the fault come back, problem solved. The car also feels smoother and seems to pull a bit harder. I did a bit of reading and others have had to change the fuel pump for the same issue - so it's likely one or the other. I'd go ahead and change the filter first, as you'll have to do that anyway for peice of mind.
 

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Good post by jcolley - the two fuses are for the high and low pressure pumps. I forgot to mention to check these first.
 

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Discussion Starter #5 (Edited)
Jcolley, I was about to rename my son after you, fuse #30 in the glove box was blown, I replaced it and went for a spin. I took 1st and 2nd to 8K and the car pulled strong. Then at about 6K in 3rd the Engine Light and "Reduced Power" message came back. I thought maybe fuse #30 was blown again but it was not, fuse #72 in the trunk is fine.

I'll run DIS/GT1 again and see if I get the same code. The car seems to run tip-top otherwise. Any other ideas?
 

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Well, glad it at least worked for a couple of gears...

So, if F30 was blown, that's the power supply fuse for the primary pump. This pump is controlled by the DME sending a pulse-width modulated signal to the EKP module over a single wire interface. As torque demand increases, the pulse-width narrows and the EKP module response by ramping up the control voltage to the primary pump (also PWM, but for power control). Above a certain demand signal from the DME, the EKP module activates the secondary pump. The secondary pump is not PWM controller, but on-off only.

The blown fuse for the primary pump is a symptom, not a cause. If you have the old one and can measure the resistance across it to verify its blown, we confirm the symptom only.

The question becomes, what blew it? I haven't looked inside an EKP module, but I would imagine its pretty straightforward. A blown fuse could indicate either a problem with the primary pump itself, the EKP module, or the wiring in between the front fuse box and the EXP module (least likely in my mind). Whichever the cause, its pulling too much current through the fuse. Whatever the fault is, it's most likely associated with the primary pump. I'm not an advocate of the "guess and swap" Easter egg mentality of troubleshooting, but if I were to replace any component first, it would be the EKP module.

There is a fuel system diagnostic function in DIS/ISTA/INPA, have you run that?
 

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I've had exactly the same issue with my m5 in the UK.

Same fault code at high revs in 3rd gear. I changed the fuel filter - didn't work. Changed the fuel pump - didn't work. Changed the ekp module and for a few weeks I couldn't recreate the fault code at all until a week ago when it's come back again.

Fuses are all ok. My last guess is battery. I'm having a high drain warning unless I disconnect the ibs.

I had a flat battery a few weeks ago after a quick startup and shut down of the car- I guess the alternator didn't have long enough to recharge the battery. Most mornings my idrive screen is dull and gets progressively brighter as the car sits and idles for a few seconds.

So my next best guess is battery but this guessing game is costing me a small fortune.

One thing to note is my engine light never resets itself. I always have to use a scanner to switch it off.
 

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Code 2788

Hi guys,
I am facing the same issue when pushing the car very hard i get check engine reduced power
The fault code is 2788
I tried almost every thing i changed the fuel pump and fuel filter
The fuel sensor that comes next to the front tyre on the left
Fuel computer
Flow meters
I fully reprogramed the car
Nothing did work
I am only having the 2788 fault code
Please any help would really be apreciated
Thank you
 

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engine malfunction

I have the same problem over here with my m5e60. I gave it a nice acceleration in M/sport mode and all that good stuff the car has, but my gear was fourth at 7-8k rpm the "engine malfunction" pop up. What is it I need to inspect
 
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