blackop555 Posted May 7, 2012 Share Posted May 7, 2012 no codes vehicle will not start with icp pluuged in. tryed a different one. still no start. with icp sensor out of head vehicle will not stall untill you ground it out on the icp sensor in the head or on the battery negative cable etc... also only wire that does this is the vref wire. i removed the signal and ground wire and it still dies out only when vref is plugged in. took the vref and spliced in a new one to egr valve vref and still will not start with icp pluuged in when its grounded. the pins have no continuity to ground nor does the vref wire. i am running out of ideas. vehicle also dies if vref wire is put to ground. Quote Link to comment Share on other sites More sharing options...
lmorris Posted May 7, 2012 Share Posted May 7, 2012 Sounds to me like you have a short to ground in your signal return wire. Shorting Vref to ground WILL shut down the truck, it's supposed to, you mess with CKP and CMP when you do that. I assume the truck runs with the ICP connector disconnected. You may want to provide a MY for this one because the earlier trucks had some chafing issues that were fixed on the newer ones. Find you signal return and over lay it back to the PCM if you don't want to go digging into the engine harness. If you still have an issue then it may be internal to the PCM. Quote Link to comment Share on other sites More sharing options...
blackop555 Posted May 8, 2012 Author Share Posted May 8, 2012 Found the problem. Was an 04. The issue was a internally shorter fuel injector back feeding somehow. Cylinder 3 Quote Link to comment Share on other sites More sharing options...
mchan68 Posted May 8, 2012 Share Posted May 8, 2012 Found the problem. Was an 04. The issue was a internally shorter fuel injector back feeding somehow. Cylinder 3I've come across a couple of those. Mind you not very many. It helps when you have a P02XX cylinder X contribution fault flagged in memory, but it sucks when you have no DTCs flagged. I'll assume that unplugging cylinder #3 injector was how you managed to restore it to a running status. Quote Link to comment Share on other sites More sharing options...
lmorris Posted May 8, 2012 Share Posted May 8, 2012 So answer me this because I am confused. How would a shorted injector affect VREF for the ICP circuit? Quote Link to comment Share on other sites More sharing options...
blackop555 Posted May 8, 2012 Author Share Posted May 8, 2012 My guess would be back feeding thru ficm to pcm if internal short. Or else it was shorting through the oil rail and feeding through the icp sensor causing the pcm to freeze up as experienced by the ids. I could be wrong Quote Link to comment Share on other sites More sharing options...
blackop555 Posted May 8, 2012 Author Share Posted May 8, 2012 Yeah unplugged it and it fired right up power balance was fine minus #3 with injector plugged in the power balance was erratic at best and the vehicle would.stall after a bit of running. Unplug the injector and it would run all day no random engine cutting out and back in like only having icp unplugged Quote Link to comment Share on other sites More sharing options...
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