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AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 25846
Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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I have an 01 silverado 1500 with a 4.8. Truck was doing fine

Customer Question

I have an 01 silverado 1500 with a 4.8. Truck was doing fine all day until i shut it off for a minute or two and it wouldn't start after that. (Crank but no start). First tjing i noticed was the fuel pump relay was buzzing. Then i noticed i was getting a false reading on my fuel guage, saying it was empty. Was thinking fuel pump. Keep in mind no previous problems existed. I also did a spark test...= NO spark. I teplaced the crankshaft positioning sensor but no luck. Inorder for me to loose both fuel and spark at the same time, I'm thinking it must be the ECU...? Out of options no idea what's going on. Please help?
JA: Does the vehicle stall at low speeds? Does it sputter?
Customer: I cant even get it to start
JA: Are you fixing your Silverado 1500 yourself? What have you tried so far?
Customer: Fuses, crankshaft positioning sensor, tested the fuel pump, ect
JA: Anything else you want the mechanic to know before I connect you?
Customer: Fuel filters are new, I've got fuel coming out when i press the needle valve on thw fuel rail
Submitted: 9 months ago.
Category: Chevy
Expert:  AMEDEE replied 9 months ago.
Hello and welcome! My name isCustomerand I can assist you with your question. Can I start by getting your Vin number? Thank you
Customer: replied 9 months ago.
2GCEK19V611108276
Expert:  AMEDEE replied 9 months ago.

Thank you for the VIN!

Expert:  AMEDEE replied 9 months ago.

Have you checked for codes in the computer?

Are you looking for possible causes?

Customer: replied 9 months ago.
no unusual codes being thrown.
Expert:  AMEDEE replied 9 months ago.

Thank you for that information.

Expert:  AMEDEE replied 9 months ago.

What did you use to check the codes in the computer?

Customer: replied 9 months ago.
Just an auto parts store obd2 reader. Nothing fancy.
Expert:  AMEDEE replied 9 months ago.

Ok we need to check for a reference voltage going to the TPS with the key in the ON position. This will verify that the computer is awake and powered up.

Customer: replied 9 months ago.
Okay, how do i go about doing that?
Expert:  AMEDEE replied 9 months ago.

With a voltmeter on the 20 volt DC scale

Customer: replied 9 months ago.
My meter only goes up to 12v...
Expert:  AMEDEE replied 9 months ago.

YES< that will work.

Customer: replied 9 months ago.
Okay, strip blue wire and find a ground right?
Expert:  AMEDEE replied 9 months ago.

The gray wire and the light blue wire going to the throttle body should have 5 volts on it with the key on.

Expert:  AMEDEE replied 9 months ago.

Another thing if you could, check for a 5 volt reference going to the MAP sensor with the key on as well.

Customer: replied 9 months ago.
The blue wire on the tps reads 44.8
Expert:  AMEDEE replied 9 months ago.

I suspect it is 4.48 volts? You only have a 12 volt battery. There is no way the TPS is getting 44 volts from the computer. If this checks out good, then we verify power to the ignition coil with the key on and cranking. We would also need to check the signal coming from the new crank sensor while cranking.

Customer: replied 9 months ago.
Should i just take a spark plug boot and put it to ground to test the coils?
Expert:  AMEDEE replied 9 months ago.

YES

Customer: replied 9 months ago.
No spark. Btw. I no longer here the fuel pump relay buzzing. Since the last time we talked ive had the battery disconnected for a while. But no, no spark
Expert:  AMEDEE replied 9 months ago.

Do the ignition coils have power going to them with the key on and when cranking?

Customer: replied 9 months ago.
No they do not
Expert:  AMEDEE replied 9 months ago.

Did you check them all? Check both banks just to be sure. If still no power, then we need to check the IGN 1 relay operation.

Customer: replied 9 months ago.
Sorry coils do have 12 volts running through the pink wires.
Expert:  AMEDEE replied 9 months ago.

Ok, good. So it sounds like the PCM is not activating the ignition coils to fire the spark. This is usually a faulty input. It could be a wiring issue from the cam or crank sensor to the computer or it could be a bad cam sensor. Was the cam sensor replaced?

Customer: replied 9 months ago.
The cam sensor was not replaced
Expert:  AMEDEE replied 9 months ago.

Ok, You might want to check and replace that sensor as needed. Also, check the wiring from these sensors to the computer. If all checks out ok and the computer is still not firing the coils, the computer is at fault and will need to be replaced.

Expert:  AMEDEE replied 9 months ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Please let me know if you have any further questions.

Expert:  AMEDEE replied 9 months ago.

Hello! It'sCustomerfrom just answer.

I am just checking in to see if you need any further assistance?

Let me know!

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