I am new to this forum and looking for some guidance: 2003 Chevy Suburban K1500, 5.3L Vortec Flex Fuel engine, 200K miles: I was driving at highway speeds and suddenly the RPMs dropped, with no response or power from the accelerator. All gauges were at normal readings (voltage =14, oil pressure = 40-45, temp = 180-190-ish). Then all gauges dropped to zero as the truck died. This is the first time it has stalled. I drifted to a stop and the truck cranks well but doesn't start. After 20-30 minutes of sitting, same response. Towed home. Dead in the water in my driveway. I am trying to diagnose the problem without throwing $$$ and parts at it. This is what I've found so far: Fuel pressure = 52 as soon as I turn the key. All fuses are good and getting power. I swapped identical relays around in the electrical center and nothing changed. Previously had a P0300 code I was trying to work through, and now have a new O2 sensor heater circuit code. Put a handheld scanner on it: O2 sensor heater circuits pass the tests (so I think this may be a false code). Engine coolant temperature is consistent with ambient temp (does this imply the sensor is working?), when cranking, scanner shows 150 RPMs (does this imply the crankshaft position sensor is working?). Battery is good, alternator is good. relatively new starter, working well. Plugs are relatively new platinum plugs, wires previously tested and withing OEM specs for resistance. Currently no spark on at least 4 cylinders, tested with spark tester and then grounded plug to engine. Coils are getting 12V @ (+) wire, but I don't think they are getting a control signal. Several ground wires connections previously cleaned and remounted with dielectric grease: ground strap from rear of engine to firewall, 2-2 under A-post to chassis/frame, one from harness on top of engine to firewall. Previously replaced the fuel lines, fuel filter, air intake manifold gasket (new one is teal), knock sensors, oil pressure sensor (didn't see/know about the camshaft position sensor or would have replaced that as well) all within the last 20K miles.

Have narrowed my quest down to: Ground wires, Crankshaft position sensor, Camshaft Position Sensor, PCM/ECM/ECU (this is the last thing I want to mess with).

Am I missing anything or any other ideas about where to go?

Thanks for sharing your knowledge/experience!

 

Did you get this figured out?
I'm having the same issue

 

There are 2 you tube videos by south main auto on crank no starts on a chevy Tahoe and an express. long videos, I d start there. That guy is great at diagnosing. and let us know what you figure out. the reduced power and stall on the road scenarios while driving are pretty scary.

did you get a check engine lite ? ( if all dash lites went out maybe it coded and threw the lite but it could nt be seen for lack of all power to the dash lites. If it coded some confirmed DTC it should auto store the freeze frame and you can retire it i there is power to the scanner port wo starting the engine .

Can you use yr scan tool now w key on engine off to pull any DTC codes and freeze frame data? Can your obdll give you PID graphs ?

I d think a crankcase position sensor would first mismatch w the cam sensor and throw a p 0336 3 sec mismatch , or a p 335 ‘no cKpos signal at all’ .code that you might see if it is a totally failed cKp s.



are you getting no fuel to all cylinders on same bank ? What is firing order ?

 

This is probably an unnecessary question, but did you put the dielectric grease only on the outside of grounds? Not on the connection itself? Cheers. Wavelength.

 

Did you figure this out, I have the same problem and I’ve come as far as you?