Keith Browning Posted September 21, 2007 Share Posted September 21, 2007 Quote: P115A = Low Fuel Level - Forced Limited PowerThe DTC P115A may set with a low fuel level input. If an excessively low fuel level input message is received by the PCM from the instrument cluster, the PCM will limit the injection control pressure (ICP). This may cause a lack of power, rough idle, or other driveability concerns. If no additional DTC's are present, the concern may have been caused by the vehicle running too low on fuel. I have seen this code before but have never experienced "forced limited power" and I assumed it meant that RPM's or fueling would be reduced. Sound like a reasonable deduction? Dead wrong fellas! How about a momentary power and RPM drop that will change frequency depending on how you change the AP position? It almost feels like an injector harness miss but not as sharp. Sure made us go looking for a problem. No codes. Good fuel pressure. All PIDs looked normal before the "misses" and the drops in RPM's were accompanied by drops in the expected PIDS.I uploaded the data to the HotLine and spent a good 45 minutes with Zach S. looking at the data together. Baffled us both and a few others on his end. He finally recommended putting more fuel in the truck and see what happens. Well, the gauge WAS on E after all!I picked this job up from one of my techs who understandably needed bailing. The truck was towed in for a no start; fuel contaminated with unknown fluid. He drained, cleaned and flushed everything. Put 5 gallons of fuel in it and spent a lot of time driving and testing to diag an EGR concern... idling and so forth. Long story short, the truck had barely an inch of fuel in the tank. (I peeked)I am a little unsure about how I feel about this one. Apparently this Forced Limit Power strategy is intentional, BUT it feels like a driveability concern! Should Doc and his team feel foolish for being fooled? What does this tell you that there seems to be no description of "Forced Limited Power," its not mentioned in any manual including the owners manual and the HotLine Engineers were not keenly aware either? Kudos to them for guessing it needed fuel and I am sure they will be surprised to get my callback tomorrow. No no no friends. I am not leaving this up to a survey. All I want to know is WHY?!?! /forums/images/%%GRAEMLIN_URL%%/boink3.gif The PCM does not limit ICP. It JERKS it down and immediately lets it back up. I know its supposed to be some kind of warning but perhaps Ford should have warned us about this? Word to the wise: Code P115A and rhythmic power loss means put some freaking fuel in it! /forums/images/%%GRAEMLIN_URL%%/banghead.gif Quote Link to comment Share on other sites More sharing options...
OHNO60 Posted September 21, 2007 Share Posted September 21, 2007 YES SIR UR RIGHT! HAVE ONE SITTING RIGHT OUTSIDE.INTERMITTENT LONG CRANK, NO DTC'S ALL WITHIN SPEC AND MIGHT YOU "LOW FUEL LEVEL" MESSAGE ON THE DASH,HAHAHA. LOOKS LIKE CUSTOMER PAY DIAG,FUEL AND A SMILE. GOTTA LOVE THESE GUYS THAT COME IN WITH BARELY ANY FUEL IN THE TANK AND WONDER WHY IT DOESN'T RUN. /forums/images/%%GRAEMLIN_URL%%/icon_crazy.gif Quote Link to comment Share on other sites More sharing options...
mchan68 Posted September 21, 2007 Share Posted September 21, 2007 YES SIR UR RIGHT! HAVE ONE SITTING RIGHT OUTSIDE.INTERMITTENT LONG CRANK, NO DTC'S ALL WITHIN SPEC AND MIGHT YOU "LOW FUEL LEVEL" MESSAGE ON THE DASH,HAHAHA. LOOKS LIKE CUSTOMER PAY DIAG,FUEL AND A SMILE. GOTTA LOVE THESE GUYS THAT COME IN WITH BARELY ANY FUEL IN THE TANK AND WONDER WHY IT DOESN'T RUN. /forums/images/%%GRAEMLIN_URL%%/icon_crazy.gifKinda reminds me of one that came in on the hook to me awhile back after I replaced an IDM (for a P1298). The SM and SA was getting ready to chew me a new asshole when I told them, "it helps when there's actually fuel in the tank" You should've seen the look on the owner's face when he was presented with the $350 tow bill and the $20 of diesel on the invoice! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted May 13, 2011 Author Share Posted May 13, 2011 I had another one this week with a P115A in memory and the driveability complaint that goes with it. This truck however has a working fuel gage and full tanks of fuel. The problem with this truck had nothing to do with the fuel level indication system at all. The PCM lost communication with the IC as evidenced by DTC U0155. The cluster was alive but it wasn't sharing fuel level data with the PCM. The network diagnostics led me to a bad IC. Quote Link to comment Share on other sites More sharing options...
Fordracer Posted May 13, 2011 Share Posted May 13, 2011 I've replaced or cleaned several fuel tanks in 6.0's and only put 5 gallons in them with no driveablity problem except for two of them. You could hold the rpm at 2000 and every 9 seconds, IIRC, the rpm would drop 500 and go right back up to 2000, it would also do it while driving and is very annoying. On the first one I had the hotline had me replacing the IPR, ICP, and the stand pipes because of the check valves. Finally one of the hotline guys noticed I had the P115A code and told me to put more fuel in it. They didn't know what was causing it but that it's not a normal symptom for the code. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted May 13, 2011 Author Share Posted May 13, 2011 5 gallons might be too much fuel depending on the tank size and the vehicle. Small variances might be the key... as for how low the fuel level needs to be, I think when the sensor voltage reaches a defined limit and remains there the DTC is set and the driveability concern becomes evident. There is no way to conclude otherwise that this is programmed into he calibration. Unfortunately not many people are aware of this condition and surprisingly few at Ford Motor Company apparently. What gets me is that in the PACED the DTC description mentions that a driveability condition may result but goes no further to explain what actually happens. Quote Link to comment Share on other sites More sharing options...
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