Been searching for an answer for hours. tried several possible solutions. looking for help.
Was driving the truck yesterday and went to start it after it sat for 10min. For a brief fraction of a second it turned over normal then the RPM of the starter turning the engine over dramatically reduced. and the truck won't start. Opened the hood to find the neg battery cable disconnected from the driver's side battery. reconnected it no change. have had the batteries checked at two places. other than the passenger side battery being low on charge the both checked out fine after charging the passenger side battery. the only error coders are p1000 and p0603 which i think are from disconnecting and reconnecting battery. checked all fuses and relays seem to work (can feel them click when ignition is turned on and starting). I hear the fuel pump running when I turn key to run. I put new starter in B/C it is only cranking at 78rpms according to the edge monitor (it's my understanding 200 is minimum for the 6.0L to start). but even with the new starter itdid not improve much 100RPM it will almost want to start sputter RPM will reach 150-200 hit 400 once It sounded like it was going to keep running but alas not. Engine parameters I've monitored are FCIM sync (1), FCIM voltage (48-47.5), inject pressure (1200), inject pulse with (2-3), engine RPM usually 75-100.
Two thinks that have me wondering after only 30 sec of cranking on the fully charged supposedly good batteries (3 mo old) there is a noticeable drop in engine RPM and the passenger side battery will draw 4 amps on the charger. I think this might be the issue when it was load tested the guy only put a 450amp draw on it. The other potential cause is when I crank the engine the Oil pressure gauge doesn't read. now I never look to see if it did while craning before but In my search for the problem one poster said to look for this as it might be a faulty oil pressure sensor causing the engine no to start. I would think this would throw a code though. any suggestions