Duramax l5p died, no start, poss fuel issue

Hi.  I have a 2022 GMC Sierra 6.6 L5p Duramax. Was whizzing down the road today at 75, felt it starting to slow, 74,73,72,71,70 even giving it gas. Then just died. I have launch scanner. It showed code P228c which is low fuel pressure regulator problem. Had it towed home. Checked for fuel contamination, changed fuel filter, flushed system as per directives.

Still not start.  Cranks away. Fuel pump is working fine.  I have attached screenshots of the live data, the only think that jumps out is the desired fuel pressure is over 7000 when it should be under 4000.

Any ideas on what to try next please. Am really stumped. TIA
                   

Check low fuel pressure with gauge from pump, then check it after low pressure regulator, maybe your sensors are bad

As I can see "Fuel rail pressure sensor 2" is too low for starting.

OK a development and a couple of questions please. I replaces fuel filter housing, filter etc. Still nothing the desired rail pressure is between 200 and 400 instead of over 3000 or 4000.

I was advises to do a fuel return test during cranking. Connect a hose to the fuel return line and crank for 15 seconds. The amount of fuel returned is supposed to be under 100ml or even under 50ml. Mine was over 500ml so possibly 10 times too much.

Any pointers on how to check if this could be fuel pressure regulator, high pressure fuel pump or an injector at fault please?

I've ordered an injector fuel return test kit to attach a tube to each injector to see if any are dumping too much return fuel.

Could just ONE faulty injector cause all this headache including no start?

Finally the low pressure fuel pump, primes to around 62psi when ignition is turned on, stays at that during cranking, but them drops within a few secods of finishing the crak. Its back to zero within 15 seconds.

Is this supposed to hold its pressure or just prime each time you turn the key?

Thanks in advance for all advice.

OK a development and a couple of questions please. I replaces fuel filter housing, filter etc. Still nothing the desired rail pressure is between 200 and 400 instead of over 3000 or 4000.

I was advises to do a fuel return test during cranking. Connect a hose to the fuel return line and crank for 15 seconds. The amount of fuel returned is supposed to be under 100ml or even under 50ml.  Mine was over 500ml so possibly 10 times too much.

Any pointers on how to check if this could be fuel pressure regulator, high pressure fuel pump or an injector at fault please?

I've ordered an injector fuel return test kit to attach a tube to each injector to see if any are dumping too much return fuel.

Could just ONE faulty injector cause all this headache including no start?

Finally the low pressure fuel pump, primes to around 62psi when ignition is turned on, stays at that during cranking, but them drops within a few secods of finishing the crak. Its back to zero within 15 seconds.

Is this supposed to hold its pressure or just prime each time you turn the key?

Thanks in advance for all advice.

low pressure pump just primes it and looks normal pressure around 5bar have seen higher pressures
rail 1 and rail 2 is definitely out of specs diesel should be reading over 200bar at start up thats over 3000psi
have you got one of them bosch cp3 high pressure pumps on engine (havnt had to deal with usa duramax engines just European v6 and v8)? they tend to eat themselfs 
i would start with measuring hpfp pressure first

---

just noticed your 7000psi rail pressure
with that pressure seems you got stuck injectors or your sensor isnt reading it right
if possible remove all injectors and just attach them to fuel delivery hoses and get someone to crank engine and check if all of them are opening and spraying