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I need help from someone experienced with GM module

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Hello, I need help from...
Hello, I need help from someone experienced with GM module communication and programming. The short story is the cluster will not wake up with ignition on while connected to the class 2 serial line, the car will not crank or run.The long version is I purchased the car wrecked in the right front and have not been able to get it running after repairs. Initially the cluster would not power up except for prndl and batt light, there was no communication to bcm with my scanner. I assumed the impact or shorted headlight wires damaged the bcm so I replaced it. Same issue.I then thought I was not programming the bcm correctly so I purchased the pcm and ipc from the same car as the bcm to eliminate the need to program. Same issue.Thinking I may have purchased a defective part I found another 2002 3.8 Monte and purchased another set of pcm, bcm, ipc with ignition switch and key. Same issue.I've traced and checked all grounds and power at bcm, ipc and pcm connectors. I've checked all fuses multiple times. I've tried to to the 30 minute relearn but can't because the ipc doesn't show the security light, only the battery light.I then found the splice pack 205 and used jumpers to eliminate modules on the circuit. The ipc will immediately "wake up" when the bcm is not connected to the serial data of the ipc. When bcm is reconnected the ipc immediately shuts down. Disconnect, immediately powers up??? It is the same condition with all 3 sets of bcm/pcm/ipc.I check for shorts on all the power, grounds and serial lines of bcm, pcm, ipc. To eliminate the possilbility of a shorted harness, I've clipped the serial lines 2 inches from the modules and run new wires to the splice pack.?????Thanks,Mike
Submitted: 4 months ago.Category: Chevy
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7/14/2017
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago
AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 26,816
Experience: ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
Verified

Hello and welcome!

My name isCustomerand I can assist you with your question.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

I am very sorry your having this issue with your vehicle.

I will try my best to answer all of your questions.

However, before we get started, please let me mention a few things.

1. If at any point you would like to speak on the phone, please feel free to request a phone call on your end and I can call you right away.

2. If you dont understand any technical terms or anything that I mention (component tests or theory or operation), please let me know and I will provide you with a more in debt explanation or answer.

3. Please understand that I am here to help you any way I can.

May I start by getting your VIN and all stored codes in the computers?

Thank you!

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Customer reply replied 4 months ago
only code is for a rear brake sensor
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

thank you.

So there is no communication with the instrument cluster yet there are no communication or instrument cluster codes?

Are you sure?

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Customer reply replied 4 months ago
please read my description. there is communication with the cluster. the cluster does not wake up however unless you disconnect the a7 serial data line
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

Ok, got it.

If you disconnect/remove the comb at the splice pack 205 then jumper pin "M" to pin "A" does the BCM then communicate?

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

I also don't see where it says you do, or do not have communicating with the PCM?

I have re read your initial post several of times.

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Customer reply replied 4 months ago
Hi. I have communication with all modules. The problem I've narrowed after isolating data lines. The cluster will power up with guages, odometer and all flashing alerts (door ajar, security, battery) only with the BCM data line disconnected. Once the BCM data line is reconnected it immediately turns off the cluster. Thank you. Mike
Customer reply replied 4 months ago
As mentioned I purchased 2 additional sets of clusters bcms, pcms and the symptoms are the same for the original and 2 new sets.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

Thank you for that information mike.

Have you checked the Class 2 serial data circuit when this occurs?

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

It might be best for us to speak on the phone.

If your willing to do so, you can request a phone call on your end and I will call you right away.

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Customer reply replied 4 months ago
No more details on phone than writing. If you dont know allow another tech more familiar to answer. Thanks
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

No problem. We can continue on this page.

Please answer my question above.

Thank you Mike

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Customer reply replied 4 months ago
Checked how? As mentioned ihave checked for shorts and ran new data lines with jumpers outside harness
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

The only correct way to check it. Using a lab scope.

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Customer reply replied 4 months ago
I dont have one. What will this show? Why would bcm turn off cluster?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

It will short out the cluster. And it will show the voltage reading on this circuit and tell us exactly what is going on.

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Customer reply replied 4 months ago
Dvom varies .10-.50v
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

You can't test this circuit using a DVOM

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Customer reply replied 4 months ago
Ok. But what will a scope show? Short? Bad module?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago
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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

YES, to answer your question, it can and will show both.. a short and or a faulty module.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

Now that you understand how the circuit works, you need to find out and locate all of the modules on this class 2 serial data circuit.

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Customer reply replied 4 months ago
I've written in my original question I've done everything you and the article explain to do with the exception of the lab scope. I have removed all data connectors and used a jumper. In absence of the scope I run new data wires, module to module of pcm/bcm, ipc while all other modules disconnected to eliminate the possibility of data line short. I've explained several times i isolated the bcm the problem turning off the cluster. Unless you can give me new information other than repeating what I've done I'd like to request a refund.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 4 months ago

I did provide you with new information. I showed you how the system works. :)

You can process a refund on your end.

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AMEDEE
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