2013 Silverado LTZ Crank but NO START Enigma

[Kenidoesit Bigg]

This is one for the ages to me.  The truck has the correct:  FUEL PRESSURE:  60psi  SPARK:  verified visually [AND WITH STARTING FLUID] correct injector pulse [verified by test light signal from ecm, test light neg to batt positive, test lead to INJ signal] and I went a step further unbolted  the fuel rail and visually verified spray from all 8 injectors].

 

THE TRUCK WILL RUN --- OFF OF STARTING FLUID

 

There is also a shrader valve on the passenger side [Fuel pressure verified and in spec 58-62psi] I used Autel scan tool to verify and slightly boost the rail presssure, STILL NO START -- IT STARTS AND DIES IMMEDIATELY, as if the injectors are being cut off.

 

The throttle body was replaced 1 year + ago, but the truck has been driving since then, using the existing thrott body... until now.

NO CODES COME UP EXCEPT THE HEATED SEAT BACK -- on a system-wide scan.

 

I did notice that if i unplug the INJector harness connector (only did the driver's side) that NO CODES will come up either,

as if the ECM doesn't care if i unplugged the harness connector to the fuel INJectors, NO MALFUNCTION REPORTS it.

 

ANY IDEAS that experienced techs with Silverado LTZ 2013 would be great if anyone else has seen this before, THANKS.

 

NO PASSLOCK MESSAGES

However I do notice that the ENGINE (symbol) STAYS SOLID WHILE CRANKING --  I dont know what this means on a 2013 Silverado, if any

thing..if anyone knows.. please HELP! 

 

I will include here more info from my notes:

 

Tools:  Autel MaxiSys

DVOM multimeter

various jumper wires

Mini oscilloscope

 

THREW AT IT SO FAR:  Crankshaft position sensor [Advance Auto, $40]

Oil Pressure Sensor (hoping it's failure was a failsafe, NOT!) Autozone $75!  OUCH!  that was NOT it!

8 A/C DELCO Spark Plugs, $7.99!  They were sludgy, but NOPE, that ain't it either! $65

 

IF I Quickly cycle the key, just BUMPS at a TIME, im sure injectors are shooting fuel when that is being done, so

after about 5 or 6 BUMPS like that, the engine will run, BUT SUDDENLY DIES when that

fuel burns .. 2 - 3 SECONDS..  Never ran into one this tough

 

 

 

 

[Kenidoesit Bigg]

I also LIVE DATA the PWM of the INJectors and the graph is iN-Sync with what is going on during cranking the engine (to start it up)  ... One quick rumble, then it  flat lines [as youre holding the key -- in crank position]

ENGINE LIGHT STAYS SOLID until the key is released.

 

THis could be a clue, but I have the slightest of what it means. AND THIS IS THE ONLY LIGHT ON THE DISPLAY WHILE CRANKING.. no other lights are on the display.

 

Edited October 10, 2019 by Kenidoesit Bigg

[davester]

maybe check fuel pressure, both when turning the key on, and while cranking the engine.  Should get up to right about 60 psi and stay there.

[CamGTP]

Do you have a spare key you can try to rule out the VATS system?

[Kenidoesit Bigg]

No, I have only one key, but I have been trying to figure IT out and newly discovered:  

 

WHILE CRANKING:

 

Vref (SOURCE) is solid at:  5.1Vdc

Crank_Signal is solid at:  2.9Vdc while holding the key.. not switching

    -- release the key, engineOFF, keyON voltage_signal is :  5.0Vdc

 

I also checked the ground_CRANK_Sensor VOLTAGE, engine off, key on: 7 mV (7 millivolts is legit, its less than the  100 mV limit)

 

THIS COULD BE AN ECU PROBLEM AS I have just replaced the CRANKSHAFT_Sensor with OEM AC Delco, $55 (returned the other aftermarket brand)

 

CRANK SIGNAL IS NOT SWITCHING IS WHERE I AM... 

 

ONLY ONE KEY, THE TRUCK HAS 82K MILES, THE KEY LOOKS OF NORMAL USAGE AND THE SECURITY SYSTEM IS NOT COMPLAINING.

      --- I am contemplating throwing a transponder at it, but 

           that feels somewhat unwise --- UNLESS it is causing the ECU

           to hold  the crank signal away from Zer0 (at 2.97V) --

           would be great to know that this is some SECURITY FEATURE, ANOTHER MODULE CAUSING IT, I FIND NO SHORTS TO GROUND OR REFERENCE ( I have unplugged several fuses, like A/C AIRBAG, HEAD LAMPS)

 

I have thought about the IGN switch, but Vref stays solid during cranking and during cranking the ENGINE SYMBOLS stands SOLID and BOLDLY by itself in the middle of INStrument Cluster.

 

ANY IDEAS WILL GREATLY BE APPRECIATED... I AM NOT GETTING ANY SECURITY CODES ON THE INST CLUSER OR MAXISYS LIVE DATA PIDS.

 

PLEASE HELP!  

 

 

 

 

[Kenidoesit Bigg]

The Security System is PassLock (whatever version that's up to now)... 

A FULL SYSTEM SCAN HAS BEEN DONE AGAIN:

  the only fault:  SEAT BACK HEATER   --- omg!  short to ground...

 

So, my next move is snatching the seat out (and unplugging everything related to the seat)

 

FIngers crossed, I'll keep yall posted, but IRON RESSURECTION IS ON NOW.

 

ITs been a week on this dumb truck, Ill be shocked if that's it -- buts it's never that simple.

 

[Kenidoesit Bigg]

FUEL PRESSURE IS LEGIT 58-60 psig -- with the ability to boost, I last boosted it to 70 or so psi with the scantool..

NO EFFECT --- ALSO, I removed the fuel_RAIL to visually confirm the fuel spray  --- 

 

I have elimated fuel delivery and found a SMOKING GUN --- CRANK SENSOR CIRCUITRY is NOT ALLOWING the signal to

switch ON and OFF ... the Signal STAYS POSITIVE, it should fall to ZERO (or very close to it, like 0.7V <effect of diodes).

 

[mjdaspen3]

Not sure how you made out, I am just seeing this now.  Any time you replace the crank position sensor you must perform a "re-learn" procedure for the ECM to recognize and pair with it.  Good luck.

Mike

[mjdaspen3]

13 minutes ago, mjdaspen3 said:

Not sure how you made out, I am just seeing this now.  Any time you replace the crank position sensor you must perform a "re-learn" procedure for the ECM to recognize and pair with it.  Good luck.

Mike

If it's yours and you break it, no biggie.  If it's mine and you break it, it's yours!

[Play Harder]

The engine must be running to perform the relearn,  remember?  Its done by "snapping" the throttle at 4000 rpm.  My truck won't even start,  but thanks for the idea.  

 

I still have yet to solve this enigma.   I walked away from it,  so far,  for about a week.   

 

I am leaning toward replacing the ECM or the transponder/receiving unit around the ignition key,  but I like to be certain as I've unsuccessfully thrown about $200 in parts at it thusfar

 

[Kenidoesit Bigg]

logged in from my other account above, but the facts that I do know:

 

The crank sensor wiring is legit; no shorts, opens and the ground checks out.

 

Oscilloscope shows the crank signal switching, but switching 5V to 2.9V

 -- this is definitely the problem, thee smoking gun

The signal should switch completely off 5V to 0V

 

The cause of this defect could be security system related or I have an ECM that is faulty... I will

Keep you guys posted... Eventually someone else will experience this same problem.

 

I am confident in the readings, because I also looked at the CAM sensor signal - using the same scope

and it's waveform is a perfect squared wave switching fully from 5V to 0V while cranking the engine.

 

ALSO... IF / WHEN I turn the crank by hand, the CRANK SIGNAL actually shows that it IS switching completely on and off (5Vdc to 0Vdc)... Thus I labeled this nightmare enigmatic.

 

Interesting problem no doubt.

 

 

[carkhz316]

Kenidoesit Bigg: It sounds like you may have solved it. My bet is since that crank sensor has obviously failed, the pull-down signal is dropping out at higher RPM beyond cranking. When that happens, injection pulse and ignition cut out, hence the start/stop symptoms above. Let us know how it goes.

[Kenidoesit Bigg]

logged in from my other account above, but the facts that I do know:

 

The crank sensor wiring is legit; no shorts, opens and the ground checks out.

 

Oscilloscope shows the crank signal switching, but switching 5V to 2.9V

 -- this is definitely the problem, thee smoking gun

The signal should switch completely off 5V to 0V

 

The cause of this defect could be security system related or I have an ECM that is faulty... I will

Keep you guys posted... Eventually someone else will experience this same problem.

 

I am confident in the readings, because I also looked at the CAM sensor signal - using the same scope

and it's waveform is a perfect squared wave switching fully from 5V to 0V while cranking the engine.

 

ALSO... IF / WHEN I turn the crank by hand, the CRANK SIGNAL actually shows that it IS switching completely on and off (5Vdc to 0Vdc)... Thus I labeled this nightmare enigmatic.

 

Interesting problem no doubt.

 

 

I WOULDNT USE THE WORD "SOLVED" JUST YET AS THE TRUCK WONT RUN --- Unless you're holding a can of starting fluid on it...spraying... Lol

 

[Michap11]

Did you ever find the issue having the same problem.

[davester]

On 12/28/2023 at 8:52 PM, Michap11 said:

Did you ever find the issue having the same problem.

Have you done any diagnosis or are you just hoping to throw the same parts at your truck, that fixed some other truck?