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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29534
Experience:  GM Grand Master Technician 2007. 14 years experience.
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04 Silverado no start

Customer Question

04 Silverado no start
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

HI there, I am Cam.
"
Can You tell me your first name?

Also with your no start, what is the history to this? Was it all at once or have you been having issues prior to this ?

Customer: replied 1 year ago.
james..ok we have a nice crank, did the test for the spark , no spark, fuel pressure is fine
Customer: replied 1 year ago.
all at once , no prior issu
Expert:  GM Tech (Cam) replied 1 year ago.

OK James, did you check spark at the cylinders or off the cow pack itself?

Customer: replied 1 year ago.
no good , run diag test on the coil have power to the pink wire..and have continues power to the same wire when cranking..replaced the single coil still no start..this is a 6 cylinder chevy..
Customer: replied 1 year ago.
when cranking we have test light connected.. the light is flashing , indicating signal from pcm
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, flashing light to indicate coil is getting ground signal. May I ask what you used for your spark tester?

Customer: replied 1 year ago.
a spark plug and ..grounded it to battery ground. still no spark
Expert:  GM Tech (Cam) replied 1 year ago.

Can I ask what you used to check power to the pink? Test light or meter?

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

IS there a remote starter installed? THE second set of wires that attach have another white wire that may be grounded somewhere else stopping it when plugged in.

Customer: replied 1 year ago.
no remote starter..which second set of wire?
Expert:  GM Tech (Cam) replied 1 year ago.

Don't worry about that then. You changed out the coil assembly and it made no change?

Customer: replied 1 year ago.
correct , we even tried the third new coil , no result
Expert:  GM Tech (Cam) replied 1 year ago.

OK so its likely the injection control module beside the coil pack or wiring. Have you checked any of that?

If I were to post diagnosis for this, would you be able to follow those?

Customer: replied 1 year ago.
no injection control module teat done..yes
Expert:  GM Tech (Cam) replied 1 year ago.

OK, its attached in this document.

Customer: replied 1 year ago.
why aren't we getting spark?we already fuel coming in..
Expert:  GM Tech (Cam) replied 1 year ago.

Yes, its in the spark system. Go through those diagnosis I posted to locate the issue.

Customer: replied 1 year ago.
I don't see your post
Expert:  GM Tech (Cam) replied 1 year ago.

Do you see the link 2 posts back?

Customer: replied 1 year ago.
I see it ,I also have a code po128
Customer: replied 1 year ago.
cam, are u there?
Expert:  GM Tech (Cam) replied 1 year ago.

Yes that code is either an open circuit to the coolant temp sensor or a thermostat that's opening too soon.

Customer: replied 1 year ago.
ok we done the tests all items chek out
Customer: replied 1 year ago.
what else
Customer: replied 1 year ago.
would that po128 code cut the ignition off and not to have spark?also when we crank the engine the RPM needle does not rise at all, to 300 or 400 rpm
Expert:  GM Tech (Cam) replied 1 year ago.

What was your cranking RPM on the scan tool what was your cranking RPM on the scan tool? ?

Customer: replied 1 year ago.
we don't have scan tool to chek rpmwe just have code reader..
Expert:  GM Tech (Cam) replied 1 year ago.

Did the code reader show a cranking RPM or you just guessed at this?

Customer: replied 1 year ago.
no,I like to just have a record to go back to
Customer: replied 1 year ago.
like I said before when we crank we don't see rpm needle risingand we cheked the power to cps with the key on very weak light but excellent ground.
Expert:  GM Tech (Cam) replied 1 year ago.

We can only check power and ground at the crank sensor, after that it’s a matter of seeing what speed the Powertrain Control Module (PCM) is seeing. Because the PCM controls the spark and such, if it does not read that speed then it won’t start. Going by the cluster is not valid either, we must see that data.

Customer: replied 1 year ago.
how about turning engine manully and with a meter reading the voltage at the crank sensor..
Customer: replied 1 year ago.
oh also need to say that we have already installed a new cps
Expert:  GM Tech (Cam) replied 1 year ago.

That still does not show what the PCM is seeing. You may be getting a proper signal, but it that circuit internal to the Powertrain Control Module (PCM) is faulty, it won't show an RPM signal and as such won't run.

I understand you don't have a scanner that can read the live data, but I cannot stress enough that we must have that in order to properly complete the diagnosis. Otherwise we will be running in circles guessing at things and likely wasting money guessing at parts to replace next.

Customer: replied 1 year ago.
since we don't have scanner then what
Expert:  GM Tech (Cam) replied 1 year ago.

Without a scanner, I am not sure how to proceed. I won't simple suggest parts to guess at unless they are cheap and you have done all of those.

Customer: replied 1 year ago.
what are the chances that pcm might be bad. so far with all this tests and partsand if pcm unit bad , if we replaced it does it need to be adopted to the car?
Expert:  GM Tech (Cam) replied 1 year ago.

There is a chance the PCM is bad, yes, but it must be programmed then setup to the vehicle. Its not something you can on your own at home.

Customer: replied 1 year ago.
I need the wirring diagram for the ignition system on this truck ..thank you
Expert:  GM Tech (Cam) replied 1 year ago.

Here it is.