My uncle has a 2004 Tahoo that is bone stock. All of the sudden he went to start it and it would run for about 5 seconds then die. I hooked up HPTuners and we were able to get it to run (very badly) for about 4 minutes so I could get a log file. It set the P0171 and p0174 codes first than after a couple of minutes the P0336 code came up. He replaced the fuel filter and that did nothing. Also STFT and LTFT are all showing very lean (high positive numbers). Any ideas on what this could be? I can post the log file if anyone thinks that would help.

 

Sounds like the fuel pump is shot.

 

P0336 is a code for the crank position sensor, it is possible that this code could have set from the engine running rough and not the cause of it running rough. P0171 and P0174 are codes for lean fuel trims which were seen. I would check fuel pressure to rule out the pump, pressure should be around 55-60psi. Also check for vacuum leaks, intake manifold gaskets are common but usually don't effect engine operation at operating temperature, only at cold startup. Additionally check to make sure the mass airflow sensor is clean and reading accurately, you should see around 5 to 7 grams per second at idle.

 

Ok so I checked the fuel pressure today and it had about 10 psi. Time for a pump. Thanks for the input guys.