2005 Chevrolet Monte Carlo Will not start

Tiny
LAWYN
  • MEMBER
  • 2005 CHEVROLET MONTE CARLO
  • 3.4L
  • V6
  • FWD
  • AUTOMATIC
  • 110,000 MILES
Vehicle was started and stopped about 6 times. It then sat for about 2 hours, when I went to leave the dash lights flickered and a "relay symphony"sound came from under the dash and the driver side fuse box. Checked battery, it is 12.5V. Car will not start so can not test further. All fuses are good and all relays tested good. Changed the ignition switch, did not help. Had BCM repaired (company I used said they repaired it) and car still doing the same thing. Code reader can not get codes, the screen flickers with the dash lights. Any ideas on what might be the problem?
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Monday, March 30th, 2015 AT 2:15 PM

11 Replies

Tiny
JDL
  • EXPERT
Are you saying it cranks good but won't start or it won't even crank? Did you check for voltage at applicable fuses or relays, use a testlight or digital multimeter.

Can you communicate with computer? If not that's where I would start. Can you force the computer to set a code just as a test? Also, with key on, check for ref voltage at any sensor that uses a ref voltage, if no ref voltage, go from there.

Does the starter crank ok?

Anybody else with any ideas, jump in.
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Monday, March 30th, 2015 AT 3:13 PM
Tiny
LAWYN
  • MEMBER
Will not crank. I put the key in the ignition and it "freaks out". Can not link with code reader.
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Monday, March 30th, 2015 AT 3:19 PM
Tiny
JDL
  • EXPERT
Right now, I think you have a computer problem. I'd have to check voltage and ground circuits at computer, go from there. Maybe the computer is trying to reset for some reason.

We can usually crank the starter, but, that doesn't mean it will start. The computer grounds the crank relay.

Did you try taking the negative battery cable loose for a few minutes and then reconnect, see if it helps?
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Tuesday, March 31st, 2015 AT 10:54 AM
Tiny
JDL
  • EXPERT
Just to add, I'd still have to double check the battery and connections.
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Tuesday, March 31st, 2015 AT 10:56 AM
Tiny
LAWYN
  • MEMBER
Yes I removed negative battery cable re-attached but there was no change.
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Tuesday, March 31st, 2015 AT 10:58 AM
Tiny
LAWYN
  • MEMBER
Going to check grounds soon. I will keep you updated. Thanks for the ideas.
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Tuesday, March 31st, 2015 AT 11:01 AM
Tiny
LAWYN
  • MEMBER
I was told that I might have a ground fault in clstr/BCM/DLC circuit. How can I check this to find out? Where is the ground for this circuit located?
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Tuesday, March 31st, 2015 AT 11:21 AM
Tiny
JDL
  • EXPERT
The ground for the instrument cluster is A4 in the diagram. Take connector loose from instrument cluster, use a test lite connected to battery voltage, touch the A4 terminal on the wiring harness connector, if the lite comes on, the ground is good.

At your datalink connector, where you plug in a scanner or code reader, pin 16 is hot all the time. Check for voltage. Pin 4 and 5 are grounds, check those also.
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Wednesday, April 1st, 2015 AT 8:51 AM
Tiny
JDL
  • EXPERT
This is your data link connector.
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Wednesday, April 1st, 2015 AT 9:03 AM
Tiny
LAWYN
  • MEMBER
Thank you so much for the info. I will let you know what happens.
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Wednesday, April 1st, 2015 AT 12:28 PM
Tiny
JDL
  • EXPERT
No problem, have a good day.
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Wednesday, June 24th, 2015 AT 10:45 AM

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