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Heck engine light. Code reader says mo link. 04 GMC 2500 HD…

Customer Question
Heck engine light. Code...

Heck engine light. Code reader says mo link

Mechanic's Assistant: Has your vehicle stalled? Has anyone run a diagnostic test to pull the trouble code?

No

Mechanic's Assistant: What is the make/model/year of your car?

04 GMC 2500 HD 8.1 has

Mechanic's Assistant: Are you fixing your 2500 yourself? What have you tried so far?

My problem is I can't read the codes because the code reader can't communicate. Its not a fuse. I have power

Submitted: 4 months ago.Category: Chevy
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Answered in 15 minutes by:
3/7/2018
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago
Don
Don, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1,746
Experience: we have a fleet of fords chev's and chyslers that i work on daily
Verified

hi there my name is don i will try to help you on this

did you check the cigaret lighter fuse ?

that is the fuse that the scanner port is linked to ?

don

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Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

Hi again what scanner do you have

?

don

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Customer reply replied 4 months ago
I have power the fuses are fine. No scanner, just a Actron code reader that works on other vehicles. Problem is with the truck not with the code reader or fuses
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

Have you tried another scanner on it ?

what is the truck doing ?

can you get flash codes with the yellow light ?

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Customer reply replied 4 months ago
I have tried another scanner
The truck has low power
I have no idea how to retrieve a flash code
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

hi there

thanks for that information let me see if i can find the information for you

please be patient

there is however a GM expert on here that works for GM his name is Cam i get request him to help you if you like

Don

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Customer reply replied 4 months ago
please
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

ok will do please stand by

don

there was no charge for my part

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Customer reply replied 4 months ago
Thanks!
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

welcome

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Customer reply replied 4 months ago
I guess we were forgotten
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

sorry i will try again

don

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Customer reply replied 4 months ago
No one can help?
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

i am trying to get some one sorry for the delay

don

can you try this and see what comes up

https://www.troublecodes.net/gm/

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Customer reply replied 4 months ago
There is no way I can get a trouble code because the computer is not connecting to the code reader.
It says "No link"
Chevy Mechanic: Don, ASE Certified Technician replied 4 months ago

hi there i finally got someone to help you he will br along shortly

thanks for you patience

have agreat day

Don

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Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 30,400
Experience: GM Grand Master Technician 2007. 14 years experience.
Verified

Hello there, I am Cam.

I am Licensed technician at a GM dealership with more than 16 years experience. 
Like you, I am a user of this website and as such, any billing questions should be sent to customer service.

I ask that you please provide details and communicate with me so we can make your experience here worth 5 stars! I am around most days but not every minute of every day. If you reply while I am offline, I will respond when I am next online. 

I am reviewing your request and will post in a moment.

With your vehicle, is the check engine light on when you turn the key on?

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Customer reply replied 4 months ago
But we need to address another problem first.I can't read the codes because the code reader can't link with the ECM.
I have power to the diagnostic port, but no link
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago
Does it work to scan other vehicles?
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Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago
If you can scan other vehicles then we need to check the data plug. Purple wire is data line,then top centre 2pins are grounds. Both need to be tested. Last is power to the pink. If those work then it’s something with the scanner.
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Customer reply replied 4 months ago
The scanner works on other vehicles.
There is power to the port. The ground are grounding.
Why do I not have data on the purple wire?
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago
Not sure. Try this, with the key off, connect the ground to the data line. Then turn the key on and try to start. Let me know what it does.
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Customer reply replied 4 months ago
Grounding the data line?? What will that accomplish
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Its a short cut test, if the radio does not come on then it tells me the data line is in tact to that plug and confirms its a problem with your scanner.
If there is no reaction from the vehicle then it tells me the data wire from the plug to the splice pack where it branches out to the various module is bad, that splice pack is just behind the data plug about 6" up in the harness.

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Customer reply replied 4 months ago
Would an after market radio affect this?
It's been installed for a year with no problem.
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Possibly yes. Aftermarket radios require a chime module to first provide the ignition power and second to provide system sounds like the chimes. If the module is incompatible with the scanner, it would not connect.

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Customer reply replied 4 months ago
It worked for a year, so I didn't think that would cause it.
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

I Cannot agree just yet. THe module may have failed internally. For the amount of time it takes, I would check first what I mentioned then second, unplug the chime module and try again.

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Customer reply replied 4 months ago
Ok. I'll try it
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Thank you. I will be on and off for the remainder of the evening, if I catch your reply I will respond, but if not then I will in the morning.

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Customer reply replied 4 months ago
Ok. Thanks
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Good morning. How are things today? Any updates?

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Customer reply replied 4 months ago
We are traveling and will get into that when we get home late Monday.
But I will follow through and let you know
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago
Sounds good.
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Customer reply replied 4 months ago
I grounded the purple wire and the truck started but died as soon as the key returned to the run position.
What does those tell us?
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Well if you remove the short and it starts and runs, that tells me the data network is good to the plug and its a problem with your scanner

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Customer reply replied 4 months ago
Why did the one at Autozone not work either?
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Ok, about the chime module did you disconnect that and try scanning again?

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Customer reply replied 4 months ago
No I didn't.
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Try that next. That is about all I have left to try.

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Customer reply replied 4 months ago
Ok. I'll try that in the morning
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

ok

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Customer reply replied 4 months ago
I disconnected the radio and still no data.
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Radio and Chime module?

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Customer reply replied 4 months ago
I disconnected the main harness, chime module and all.
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Ok, recap, ground purple, it starts/stalls, no connection, starts and runs fine, that means data line is good.
Test light to pink wire in 16, you get full power, as bright as testing battery.
Test light to positive, you get ground in BOTH top centre pins, correct?

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Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

Ok, so everything says its a scanner issue. Did anyone try to connect whit the ABs module or Body control module?

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Customer reply replied 4 months ago
Nobody did
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

I would try that next. At the moment everything is pointing towards the scanner since the wiring checks out and the modules are talking to each other.

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Customer reply replied 4 months ago
Ok. I'll go to town today and get another scanner and will check back with you this afternoon
Chevy Mechanic: GM Tech (Cam), Chevy Technician replied 4 months ago

ok

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