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sprinkles08
sprinkles08, ASE Certified Technician
Category: GMC
Satisfied Customers: 22657
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have a 2001 GMC 3500 with a Duramax. When I plug a scanner

Customer Question

I have a 2001 GMC 3500 with a Duramax. When I plug a scanner into the ODB2 port it will power up the scanner but won't communicate with the ECM. I checked the cigar fuse under the hood and it is fine
Submitted: 9 months ago.
Category: GMC
Expert:  sprinkles08 replied 9 months ago.

Hello and welcome to JustAnswer!

You don't mention what problem you're trying to diagnose but if the ECM does not communicate then I would suspect you're trying to diagnose a no start condition. If the engine doesn't start and communication isn't possible then the ECM is down, either due to an internal failure or a loss of power or ground to it.

Does the engine not start?

Customer: replied 9 months ago.
The truck starts and runs fine, I have a Diablo tuner for it and it won't communicate with the ECM. I purchased another tuner and it has the same issue, previous to this it worked fine
Expert:  sprinkles08 replied 9 months ago.

There are no actual symptoms then?

Customer: replied 9 months ago.
Nothing other than my programmer will not communicate with the ecm, meaning I can't put any of the tunes from the programmer into the ecm
Expert:  sprinkles08 replied 9 months ago.

Do you have access to a scan tool or code reader? You're going to need one to see if communication is possible that way.

Customer: replied 9 months ago.
I have a scan tool also. It powers up all 3 of them but will not communicate with the ecm
Expert:  sprinkles08 replied 9 months ago.

They have each been successfully used on this vehicle prior to this? What is the brand and model of each?

Customer: replied 9 months ago.
Diablo sport tuner, super chips cortex and the scanner was my friends it was a snap on scanner all 3 have been used on this truck before. I cleaned all the contacts on the ecm and the ODB2 port
Expert:  sprinkles08 replied 9 months ago.

So one actual scan tool then.

Has any actual testing been done?

Customer: replied 9 months ago.
No
Expert:  sprinkles08 replied 9 months ago.

Was the scan tool used to attempt communication with any other modules?

Customer: replied 9 months ago.
Nope
Expert:  sprinkles08 replied 9 months ago.

The problem is either internal in the engine controller, a poor connection at the data link connector, or there is a wiring problem between the data link connector and ECM. If there are no visible problems with terminals then the communication circuits will need to be connected and if ok then the ECM can be condemned.

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