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Daniel Wilson
Daniel Wilson,
Category: Chevy
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Experience:  Owner at DJ Wilson
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I have a 1996 C3500 6.6 Diesel, Three scan tools will not

Customer Question

I have a 1996 C3500 6.6 Diesel, Three scan tools will not communicate with the truck. One thing I found is that the number 5 pin signal ground is not grounded. Can I run a new ground for this pin.
Submitted: 6 months ago.
Category: Chevy
Expert:  Juan Crespo replied 6 months ago.

Hi there.

Perhaps I can help. Can I ask what is it you're trying to diagnose?

Customer: replied 6 months ago.
My scanners with not do any kind of diagnose with the truck all 3 will power on but no communications. same as my first question.
Expert:  Juan Crespo replied 6 months ago.

Based on your reply, I don't think I can help you. I'll opt out so others can try. Please don't rate or reply until another expert responds or the site will cycle this back to me.

Expert:  david craig replied 6 months ago.

Hi Im David , so you're not getting a ground on pin 5 of the dlc?

Expert:  david craig replied 6 months ago.

hello?

Expert:  david craig replied 6 months ago.

do you still need assistance?

Expert:  david craig replied 6 months ago.

hello?

Customer: replied 6 months ago.
i still need help was out of town for a few and no ground on pin 5 of dic
Expert:  david craig replied 6 months ago.

OK. im going to pull up a print and we'll get this thing fixed.

Customer: replied 6 months ago.
sounds good to me this truck is driving me crazer
Customer: replied 6 months ago.
the main thing that I need is for the abs pump to cycle to bleed the brakesBut the new scaner that will do the job will not connect to the truck
Expert:  david craig replied 6 months ago.

ok. there only thing it says for 5 is its a signal ground and doesnt show where it goes. it obviously has to go to the pcm so ive attached the pcm pin outs and the only grounds are on connector c3. i believe thats going to be where it goes.

Customer: replied 6 months ago.
Thanks for your help will check it out tomorrow and will let you know what happens.
Expert:  david craig replied 6 months ago.

you're welcome. its gotta be broken between the dlc and pcm

Expert:  david craig replied 6 months ago.

any luck?

Customer: replied 5 months ago.
sorry about the late response but I had a radiator tank split and I got second-degree burns on my right arm,so I have not been able to work. I am starting back to work on it today. Will let you know when I find the problem.
Customer: replied 5 months ago.
I check the ground wires on C3 # 6&7 and they are grounded
Expert:  david craig replied 5 months ago.

ok, let me get home and ill dig in ti this

Expert:  david craig replied 5 months ago.

gotta hit the sack. ill be back on tomorrow morning.

Customer: replied 5 months ago.
when are you going to answer my question
Expert:  david craig replied 5 months ago.

sorry, been in hospital with 4 tia's ......ill opt out and let another tech answer. please dont respond back as it will send the question right back to me.

Expert:  Daniel Wilson replied 5 months ago.

Hi my name is***** will be glad to help. When you say #5 is not grounded.... What connector and what pin exactly? C1. C2. C3, etc? Pin A5, C5, D5, etc? Let me know

Customer: replied 5 months ago.
5 on the obd port my scanners will power up but no communication with the the truck
Expert:  Daniel Wilson replied 5 months ago.

Thanks for the update. #4 and 5 should be grounded. Yes you can run a separate ground to see if it resolves your problem. Let me know

Expert:  Daniel Wilson replied 5 months ago.

Click here for the pinout.

Customer: replied 5 months ago.
I ran new wires to pin 4&5 to ground but still no communication with the the truck
Expert:  Daniel Wilson replied 5 months ago.

If you have power at 16 then check the wiring for the data connections between the PCM plug and the diag connector for continuity.

Expert:  Daniel Wilson replied 5 months ago.

if okay then I would have to say it is an ECM/PCM problem

Customer: replied 5 months ago.
16 has power can I run a wire from the obd port to the PCM . If so witch plug and wire do I use