Hi everyone ive been lurking for some time now and have found this site very informitive but i need some help with this one and cant find any remotley the same .
05 gmc sierra 4x4 LS1
had a bad lifter and overheated
fixed it by replaceing the cam with a performance cam
spec .515 in .522 ex .050 duration 206 in 212 ex
replaced oilpump meling, lifters melling,oem replacement heads w new bolts
and all new gaskets and seals.
heres the rub she wouldnt start before all this due to very low compression (overheated im assumming ) had a water leak from the y pipe. and now it will start and die immediately first set of codes i got was p0101 (maf) p0336 (crank sensor)and p0101 ( Sensor Reference Voltage "A" Circuit/Open)replaced the CPS p0336 went away and it started for about a sec then died and still does this
i can remove the maf wire and there is no change i have replaced it no change tested the wire i have 12.8 vdc at the power wire ground at the ground 4.8 vdc at the com and 2.8 on the out to com tests the same as the old one so i replaced the throttle body still no change
i just put a noid light on the injectors and it flashes fast when i say fast i mean mabe 4/6 time per revolutoin of the crank. oh almost forgot had my fuel presure guagde on it since the first and it has stayed at 50 to 52 psi cranking or idle i say idle but it has idled such a short time i cant even get to a point were i can see if it drop if you press the throttle

 

sorry the third code is p0641

 

for a stock vehicle you cannot do this, not without reprogramming the engine computer (i.e. PCM - powertrain control module). The first thing I would expect to see after doing something like this is DTC P0101.

https://www.obd-codes.com/p0101
Basically this P0101 diagnostic trouble code (DTC) means that there is a problem with the Mass Air Flow (MAF) sensor or circuit. The PCM detects that the actual MAF sensor frequency signal is not within a predetermined expected range of the calculated MAF value.

This will happen because a different cam shaft will result in different amounts of air flowing into the engine... which first passed through the MAF where it's measured so the PCM can then calculate how much fuel the injectors should shoot in. I don't know oem camshaft specs for your engine, and whether your new performance cam is different enough to cause a drastic enough airflow change at idle after being started to trip a P0101 code. I certainly would expect P0101 to happen before you got to the gas station.

p0641 is a generic sensor open voltage, meaning the wire/plug is not plugged in to the sensor. And p0336 is a range performance error for the crank position sensor (CKP), just like P0101 is for the MAF. I suspect the P0336 might be due to your new cam- if there was a reluctor wheel on the old OEM cam and you motor also as a Camshaft Position Sensor (CMP). Camshaft rotates at half the rate of the crankshaft, so the PCM should see signals from the cam and crank sensors accordingly. When the cam speed is not twice that of the crank, various trouble codes will be set. When it is momentary and minor, that's how a misfire is detected. And of course the other likely scenario after pulling cylinder heads and changing a camshaft is to either have damage some wires or electrical connections, or missed plugging some back in.

 

I've put much larger cams in these engines without any programming and not had any issues getting them started. That cam is basically a drop-in cam.


Do another compression test.