Greetings All,
I have been a Power Stroke owner since '99. I currently own a '12 F350 w/6.7l diesel (bought new) and it now has +/-230k miles.
On my way back from Phoenix last Monday (freeway driving, +/-75mph, truck only, no trailer), the Reduce Engine Power warning came on but the power was NOT reduced. The CEL did NOT come on and I can find NO CODES with my mini-max tuner. REP light goes off when I acknowledge it (pressing "OK" with button on steering wheel when REP warning is on) but will return at each start-up. Really, I'm not seeing any symptoms other than the REP warning, and associated anxiety about the truck reliability moving forward. Since this started happening, the truck is also now telling me that an oil change is coming due soon. I suppose this would align (anecdotally) with possible filter restriction, but I would think that any reduction of fuel pressure would throw a code.

The truck was dltd last April (about 15-20k miles) ago because I got tired of replacing the reductant heater. There were some issues with the tune install and a new PCM (reman from an outfit in Florida) was purchased and installed. The truck has been working well until recently. A couple months ago the truck began to stall when letting off the accelerator pedal. This was intermittent, and sometimes CEL would come on and with that I got several codes. Low Rail Pressure, High Rail Pressure, and Pressure Controller Fault. I have the S&S Disaster Prevention Kit (installed with dlt) and found no metal in any filter (changed them all, and cut them open) prior to taking to mechanic. Mechanic found issue with pressure control and replaced it. This resolved the issue. Now, about 3k miles later, the truck is displaying the symptom described above. It may be of interest to note that my trip "A" MPG (post dlt) was 19-20, and now the truck is usually indicating 16-17. I reset trip "A" with each fuel fill, so the indicated MPG is for each tank full.
I am a bit concerned about the reliability of aftermarket parts (computer related) and was reluctant to alter the truck for this, and other reasons. Is this just something that I need to put up with, or is there something repairable going on, even though it is NOT throwing codes?
Any help would be appreciated. I look forward to responses from the Forum members.

 

Have you checked the bottom side of the top cold side inter cooler hose. They have been known to crack.

 

I have no idea what the tuner programs do to lie to the computer? Whether that is why you have no cel? Is the computer seeing an issue? But the tune is suppressing it? No one on here know either or even if they do they are not
goi to say they do for obvious reasons.

Now, two things on my truck (which is still stock) that would sometimes act close to that. MAP sensor and CP4 pump.
My gut feeling is your pump is weak, I think till you are all done and it running right with the miles and age you have you will have 8 new injectors and a pump.

 

this is easy to check

get Forscan and check requested high fuel pressure vs actual. At idle it’s a tad bit over 4300. Check it a various rpms.

on a good pump the numbers are tight.

take a look at third row below. I think this was at 900 or 1000 rpms.

if your pump checks out…inspect the underside of the cold side charge air pipe.

map sensors are always a problem…they clog up…but usually it’s a mpg pisser .

cheers




edit… also..for injectors…check contribution balance for each injector. I think from memory you can see what the pcm has to add to the injector or take away to keep the spun in balance. Used to be if you were off by more than 20, would indicate a worn injector.

but double check the numbers and the pid, it’s been 5 years since I dabbled in this area of trouble shooting…concept is about right but details may need to be polished.

good luck

 

I will look at downloading Forscan. I have wanted to have something like it for a while now, and I really see the need for it now that the truck is having so many issues.

Certainly one must admit that this is possible, yet previously I have had several codes, all relating to fuel pressure issues (see my original post), so I don't see why the truck would not display them now.

I have not done this yet.

Thanks for the replies so far!!