Hunter of Trolls
Join Date: Nov 2012
Location: east coast
Thanked 175 Times in 136 Posts
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my issue was a bad fuel rail pressure sensor..
this is what I learned specific to that issue: the engine reduces power, disallows functions such as cruise control, and cranks torque management way up.. you simply can't get power to the terra.. reasoning: the FRP sensor is the only sensor that tells the PCM those figures (literal pressure of fuel in the fuel rail).. w/o it, it runs on pre affixed scripts/tables for operation.. it is basically running in 'open loop'.. because the pcm lost it's primary indicator of how to trim the duty cycle of injection (how long the injectors are open), it can't be sure if it's trimming correctly- so, it instead relies on a pre-determined running condition prescribed in 'limp mode'...
I figure the same holds true for other sensors, too..
every key cycle the PCM runs a BIT (built in test) to test vital functions.. If they check out, the PCM removes any limitations to the engine/powertrain.. if something doesn't check out, it tosses a code.. if something is iffy- it stores a 'pending code', and monitors carefully.. I knew my issue was electronic, as the BIT tripped a P0192 less than a second after the key was turned.. In your situation, it sounds as if a sensor is either on it's way out, OR, the sensor is fine, and what it's there to monitor is an issue..
w/o a code, it's going to be pretty dang hard to speculate..
edited to speculate anyway, because I just can't help myself sometimes:
you stated you had the dealer change fuel filters.. did the tech who did this have any experience with diesels? was he or she aware that the system needed to be primed before launching it? Air can easily enter the system- way down deep in the system, as in past the HPFP/fuel rails deep.. it can take a decent amount of time to expel it.. if the truck was starving for fuel, it absolutely would limit power..
this is the absolute ONE time a regen isn't a bad thing imHo. asking more from the fuel supply system allows it to work harder, and likely purge the air faster..
since I like to gamble, I'm going to wager you had air in your system and are likely fine as frog hair now..
Last edited by drewactual; 01-09-2013 at 08:51 AM.