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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Truck will stall. happens hot or cold. When it does stall

Customer Question

Truck will stall. happens hot or cold. When it does stall the gauges drop out and then imediatley come back. Except tach as engine is off. When this happens all other acc, hvac, lights are unaffected. Engine may restart immediately or you may have to wait 5-10 minutes as it will crank/start/stall. There are no DTC's. When it was in the muti day intermittent state I replaced the crank sensor and it did not reoccur for a week. When It came back I tried to perform a cam/crank learn and the vehicle stalls in the 3-4k rpm range. I have checked for power and ground dropping at the pcm when it stalls, all ok. have checked grounds and fuse panel connections, all ok. A used motor was installed 2k ago by another facility.
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I Am Cam. Can I get your first name please?

What year and engine is in your truck?

Customer: replied 1 year ago.
Matt 2001 Silverado 3500 dually std cab 6.0liter auto trans
Expert:  GM Tech (Cam) replied 1 year ago.

Do you happen to know what brand of crank sensor you installed?

Customer: replied 1 year ago.
GM
Expert:  GM Tech (Cam) replied 1 year ago.

Very strange, OK, what is the condition of the connector going into the sensor. Was there corrosion? Stretched terminals?

Customer: replied 1 year ago.
Looked good appear tight and clean.
Expert:  GM Tech (Cam) replied 1 year ago.

Does it lack power at any time? Is there a remote starter installed on this vehicle?

Customer: replied 1 year ago.
Runs perfect. No remote starter.
Expert:  GM Tech (Cam) replied 1 year ago.

I would consider getting warranty on your sensor as it sounds like its failed again. To work perfectly for a couple weeks then fail suggests its bad again.

Customer: replied 1 year ago.
Replaced crank sensor, no change. Replaced Crank sensor connecter with new GM connecter, no change.
Expert:  Gary replied 1 year ago.

I am sorry for the long wait

new expert here did you still need help ?

Customer: replied 1 year ago.
please.
Expert:  Gary replied 1 year ago.

can you be 100 % sure these grounds are clean and tight especially the one at the top back of the intake manifold

Customer: replied 1 year ago.
Have had them off and cleaned 3 times already.
Expert:  Gary replied 1 year ago.

what bothers me is the gauges going out

will this act up enough or long enough to test some voltages at a few fuses ?

Customer: replied 1 year ago.
That has been a concern of mine from the beginning. Which fuses do you suggest?
Expert:  Gary replied 1 year ago.

when its acting up it would be great to know what the volts are at fuses IGN0 and IGN1 in the inside fuse box

i am really leaning towards an ignition switch causing these problems

Customer: replied 1 year ago.
Will do. But i have swapped the switch with a none good one. Since the hvac and radio don't drop out I have not looked at them any further.
Expert:  Gary replied 1 year ago.

ok lets see what those 2 fuses read when its acting up

Customer: replied 1 year ago.
NO voltage drop on either fuse.
Expert:  GM Tech (Cam) replied 1 year ago.

Hey Matt, I am Back. I have a question, when it does not start after it stalls, will it fire if you put some fuel in the throttle body?

Customer: replied 1 year ago.
Never tried it Fuel presure after stall is approximately 50 psi. After stall the engine seems to catch for a split second. Long enought that you let off the key because you think it has started.
Expert:  GM Tech (Cam) replied 1 year ago.

Lets try it and see what happens.

Customer: replied 1 year ago.
Does not restart with fuel added into the plenum.
Expert:  GM Tech (Cam) replied 1 year ago.

Do you have a scanner that can read cranking RPM?

Customer: replied 1 year ago.
No. Battery has been checked and there is no audible difference in cranking speed between start and no start rpm.
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, its not the cranking speed I am concerned with, rather what the computer is seeing for cranking speed. On another note, have you checked the cam sensor at the top back of the block yet?

Customer: replied 1 year ago.
Cam sensors are under the intake. Connecter on top is clean and tight. When the engine would not restart yesterday I swapped the PCM with one I am using for a 6.0 swap into it. Started right up but I had a security and reduced power warning on. The other CPM is for 02 Escalade 6.0 and 4L60E 4wd.
Expert:  GM Tech (Cam) replied 1 year ago.

No, the 2 knock sensors are under the intake, the cam sensor is at the very back top of the engine block and there is only one.

Expert:  GM Tech (Cam) replied 1 year ago.

It would seem your PCM is the issue then. You need to replace it then perform the theft released. Many part stores will sell you one programmed to your vin. After that, it only needs a theft relearn.

Turn the key on and attempt to start the car, It may crank, it may start and stall or it may do nothing at all, this is fine, still cycle the key to start then release the key back to run. Wait 10 minutes with the key in run. The passlock light should be flashing and the DIC will say "Service Vehicle" or "Security" or have a picture of a car with a lock during that 10 minute span. After 10 minutes has passed, turn off the car, count to 10, and try to start it again and release the key back to run. Wait another 10 minutes. After 10 minutes, turn car off 10 seconds and try to start again and release the key to run. Wait another 10 minutes. After 10 minutes, turn car off 10 seconds and try to start again. It should start up this time. The passlock has been learned. During this process, turn the fans off, radio off and cycle the headlights off so the battery will not go dead. If needed, use a battery charger.

Customer: replied 1 year ago.
PCM Made no difference. Also swapped cam sensor and verified wiring.
Expert:  GM Tech (Cam) replied 1 year ago.

So we must have a wiring issue around the Pcm then, possibly under the fuse block. Its very strange that it worked after putting in a different PCM but not a new PCM.

Customer: replied 1 year ago.
Working is only idling and with security and reduced power warnings. I did not leave it running for more than a minute as it would not move out of it's own way.
Expert:  GM Tech (Cam) replied 1 year ago.

OK, have we revisited all of the grounds on the engine?

Customer: replied 1 year ago.
I added extra grounds before contacting the 1st person.
Expert:  GM Tech (Cam) replied 1 year ago.

IT goes beyond adding grounds to making sure the ground wires that attach to the engine are good. Having good grounds from the engine to the body and battery are important.

Customer: replied 1 year ago.
When the added ground goes directly to the battery I believe we can say there is a good ground connection.
Expert:  GM Tech (Cam) replied 1 year ago.

OK, I would agree the block is grounded then, but the PCM and such ground to the block in a different place, so if the connections of those wires to the block are bad, it would cause an issue.

The replacement engine, was it the exact fit? Ordered for your VIN or a wrecker engine?

Customer: replied 1 year ago.
I spoke with the installer. Used engine VIN matched by a local dismantler. All sensors were swapped from the original engine.
Expert:  GM Tech (Cam) replied 1 year ago.

I am not sure how to direct you now. I am positive I could get it if I was sitting there with my scanner, but in the absence of that, I am not sure.