Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
The fuel pump wiring behind the glove box was already inspected right?
Looking over the schematics there are only two things left that I can think of the check:
The engine will put it self in reduced power mode if it thinks the PTO is activated.
Backprobe the Power Take Off (PTO) input Dark Blue wire, circuit #538 with a Digital Volt Ohm Meter. Watch the voltage on this circuit when the condition is present. If the voltage drops low, the PCM will "think" that the PTO is engaged and reduce engine power.
The high pressure fuel pump uses oil presure. If there is some kind of oil pressure loss, either a restriction in the oil system from the oil filter or low quality oil it could be causing the high pressure fuel pump to cut out.
Check engine oil level. Verify engine oil pressure. Check the Injection Actuation Pressure Sensor wiring and voltages. The Orange wire is 5 V reference from the ECM. The Yellow wire is ground from the ECM. The Green wire is the signal voltage from the sensor to the ECM. The sensor signal voltage should change relative to engine oil pressure. Connect an oil pressure gauge (capable of 5,000 PSI) to the oil pressure test port on the high pressure oil pump. Compare actual oil pressure to indicated oil pressure in scan data (if you have a compatible scan tool).
I just wanted to check whether you need any additional help.
If you no longer need assistance, please don't forget to rate.