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Discussion Starter · #1 ·
So I took my truck to the dealer today because they seemed to have the most competent diesel techs nearby... I had them basically run diagnostics and generally inspect my truck because I have been getting 7 ish mpg and I am stumped as to why. I was told that they did a DRB scan and found out that "the computer sees that turbo is at full boost full time causing overinjection of fuel".
Maybe I'm missing something but I thought that the injection of fuel had absolutely nothing to do with a computer. Also, just out of curiosity I did the on off on off on and checked my pcm fault codes and got code# 55 right off the bat as if there were no faults.
Can anybody help clarify this? Am I getting a load of BS from the dealership or am I being an idiot?
 

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the dealership is blowing smoke up your azz...

Your correct, the PCM (these things dont even have an ECM) controls only very basic functions such as grid heaters, charging and auto trans controls. It doesnt, and cannot have anything to do with the operation of the engine as the engine is completely mechanical


Super bad mileage like that is usually not hard to figure out knowing any other symptoms. Could be slipped timing, bad injector(s), hole in intercooler boot, ect...
 

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Discussion Starter · #3 ·
No excess smoke, good fuel pressure, new overflow valve, new prefilter screen, newer fuel filter, making good boost, normal EGTs, normal power, easy startup and idle, trans temp is fine, and I didn't find any boost leaks.
I'm going to have to find that mechanic and chew him out tomorrow I guess.
 

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Dealer "mechanics" are totally useless on these all mechanical engines.
Without the computer to tell them what's wrong they are lost and most times blame the problem on a bad $600 PCM.
 

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Dealer "mechanics" are totally useless
Without the computer to tell them what's wrong they are lost and most times blame the problem on a bad $600 PCM.
Corrected for truth ;) LOL

How much do you idle the truck? Alot of people cry about winter mileage and they dont even think about how much fuel is being burnt while idling!
 

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Discussion Starter · #6 ·
I promise i dont idle away well over half of my fuel. Haha. What seems to have happened was the mechanic told the head guy that the wastegate actuator was broken and the head guy somewhere in there assumed the computer was involved... I talked directly to the mechanic who worked on my truck and he seemed to know what he was talking about to the point that he knew the motor pretty well.
 
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