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Mike V.
Mike V., Auto Technician
Category: Chevy
Satisfied Customers: 25498
Experience:  25 years automotive experience, Certified Subaru Tech and Nissan factory trained.
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Chevrolet Monte Carlo LS: good morning, My name is XXXXX XXXXX

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good morning,
My name is XXXXX XXXXX I have a 2001 monte Carlo that will not crank over.
Hello and thank you for your question today!
I see there is power on the pink wire and the y/b wire.Is the battery voltage on the y/b with the key in the start position?
Also, what color is the wire for term 87 and 30?
The wiring diagram isn't giving me the numbers for the relay terminals.
let me know
Customer: replied 3 years ago.

Yes bat voltage on y/b wire key in on and start position. #87 ppl to starter

#30red bat voltage from the fuseible link

Ok, check the pcm crank fuse in the fuse box inside the car. Make sure there is power to both sides when the key is in the start position and let me know.
It should be labeled as such.

Customer: replied 3 years ago.

Yes there is power on both sides of the PCM crank fuse which is 10 amps in the start position

Ok, here is the thing, the pcm is suppose to be grounding your starter relay and it isn't.
This means it's possibe the y/b wire is broken or the ecm is no good.
One other thought would be the neutral safety switch on the transmission. It's not shown in the wirng diagram, but in most cases the car has to know it's in park before the engine will crank. If you jumper pink and purple, this should make the starter at least crank the engine. From here looking at the wiring diagram, I suspect the next test to do would be to check continuity on the y/b wire from the pcm to the relay.
Customer: replied 3 years ago.

Ok there is cont. from the pcm y/b wire to the relay socket y/b wire and the engine does crank from pink to purple wire. how do i determine if the neutral safety is bad or the pcm. pcm seems to be doing its job

You might be able to tell by turning the key on and then see if it indicates on the dash what position the switch is in.
Otherwise, check for continuity to ground on the white wire and the green/white stripped wire off the switch on the transmission.This would mean the switch is doing its job and telling the pcm the car is in park. If it is, then the pcm is not doing it's job which is to ground the relay on the y/b wire so the starter will crank.
Customer: replied 3 years ago.

Ok with the key in the off position I have cont. on the wht wire, but when I turn the key to the acc or on position the cont. breaks, could it be a bad neutral safety sw?Not sure if it is suppose to stay with the key on? Also no grn/wht wire. sounds like it could be a bad ground somewhere like you said.

Not sure on the switch having continuity with the key on.
It's not a bad ground though, it's the pcm not making the ground when you turn the key to start the engine. It's suppose to ground the y/b wire and activate the relay to put power to the starter solenoid,it's not doing that. It seems to be the pcm that is the problem.
Customer: replied 3 years ago.

Ok I guess i will check all the grounds from the pcm and see if I can find one open. Other than that one last thing according to a GM check sheet I probed between the bat. terminal side of the relay to the yel/blk(control side of the relay with a DMM and put the key in the start position and saw -12.84 v. Thank you for your help Mike I appreciate it very much.

What did you have before you turned the key to the start position?

Customer: replied 3 years ago.

0 volts

That indicates it is going to ground as it should. First open, then when it grounds it will show battery voltage. Have you tried swapping the relay with another relay like it?

Customer: replied 3 years ago.

yes and I tested the relay all good

Ok, I would like to have you run this test for me please:
Put the relay in and check for power on the y/b wire with the key off, then on.
Then, turn the key to the start position and see if there is voltage there.
Please run this test and let me know what you find, Thanks

Customer: replied 3 years ago.

Voltage at the yellow black wire with the key of is negative 96.7 milli volts voltage on the yellow black with the key on or start is 5.5 voltage same voltage in on or start position

Customer: replied 3 years ago.

Mike I have full battery voltage on the yellow black wire at the PCM with the relay in if I pull the relay and measure voltage at the yellow black on the PCM I have zero voltage both times with key in start position

Ok, that makes sense, but then when the relay is in and you go to the start position it's dropping to 5.5 volts on the y/b wire?
Customer: replied 3 years ago.

Disregard that I have full battery at PCM yellow black and yellow black at the relay with the key in the on or start position voltage does not change 12.8v

Ok, it's the pcm, it should drop to 0 volts when the key is in the start position.
That seems to be the problem here.
Please be sure to let me know if you need further assistance, if not, please be sure to rate my answer. If you got here on the free trial, your card will not be charged.
Thank you.
Customer: replied 3 years ago.

Mike thank you very much for your patience and your expertise I appreciate it very much and will leave feedback for you have a great day!



You are very welcome and wish we had a better answer for you, but at least now there is an answer. Thank you for rating, I appreciate it very much!
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