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I have a 1999 gmc 7500, 3126 cat engine, Vehicle has no

Customer Question
start signal at starter, good...
I have a 1999 gmc 7500, 3126 cat engine, Vehicle has no start signal at starter, good voltage to and out of ignition switch.
Ignition switch and starter are new.
I need a diagram of where this wiring runs and what else it may go through. its yellow at ignition and brown at starter, I'm an automotive guy and GM is suppose to be purple!!! I'm lost
Submitted: 2 years ago.Category: Medium and Heavy Trucks
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Answered in 1 hour by:
2/29/2016
Technician: Daniel Wilson,
 replied 2 years ago
Daniel Wilson
Category: Medium and Heavy Trucks
Satisfied Customers: 6,770
Experience: Owner at DJ Wilson
Verified

Hi my name is ***** ***** or manual transmission? what make and model transmission? could be a clutch switch or neutral safety. Let me know

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Customer reply replied 2 years ago
manual, and the only switch I can find on pedal I have bypassed via jumper. still no signal,
Technician: Daniel Wilson,
 replied 2 years ago

Does the check engine light come on and cycle with the key on?

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Customer reply replied 2 years ago
it does, and vehicle runs fine when you "jump Start" the starter with a remote switch. is there a secondary clutch switch , if so it would have to be way up high like behind the instrument cluster.
Technician: Daniel Wilson,
 replied 2 years ago

Click on this link and see PDF page 2 for the diagram. check the wiring for the intake heater and fuse. Also check the inline fuse/breaker and harness between the battery box and ECM. The schematic on the engine side will help.

Schematic

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Technician: Daniel Wilson,
 replied 2 years ago

There should be a PTO/ park brake switch ... see if the engine PTO control works and the RPM can be raised with the cruise switches

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Customer reply replied 2 years ago
it can
Customer reply replied 2 years ago
fast idle and pto are non factory on this chassis
Customer reply replied 2 years ago
intake heater comes on as it should also, all fuses and circuit breakers check ok,
Technician: Daniel Wilson,
 replied 2 years ago

Thanks for the update. Are there any fault codes logged in the ECM? So you do not have cruise set/resume in the dash to pull flash codes? If not is there a diagnostic switch?

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Technician: Daniel Wilson,
 replied 2 years ago
Ask Your Own Medium and Heavy Trucks Question
Technician: Daniel Wilson,
 replied 2 years ago

What is the complete model and serial number prefix of the engine?

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Customer reply replied 2 years ago
No flash code, just blink slow steady. Ready function I do believe. The more loom I pull apart the more broken wires I'm finding
Esn #7as64300
Core AR #1373531
AR#1669473
Technician: Daniel Wilson,
 replied 2 years ago

thanks for that. Where in the harness? Engine or chassis/cab?

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Customer reply replied 2 years ago
I just wanted a diagram for a 99 c7500 and got a diagram for a bus. I appreciate the try but I don't need the help offered. Thanks.
Technician: Daniel Wilson,
 replied 2 years ago

The engine schematic is the same whether it is in a bus, pete, international, kenworth, ford, or GM. The chassis connectors all plug into the OEM connector. I have the engine schematic and that is why I asked for the prefix so I can be sure you get the right prefix diagram for your serial number.

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Technician: Daniel Wilson,
 replied 2 years ago

I will opt out since you dont need the help.

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Customer reply replied 2 years ago
Ok thank you
Technician: Jeremy, Certified Truck/Bus Technician replied 2 years ago
Jeremy
Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3,776
Experience: ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
Verified

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made. No rate, site gets it all.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

CLICK HERE for the diagram. It is yellow coming off the ignition switch.

__________________________________________________________________________________________________________________________

You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see,

touch, smell, hear the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.

Once an answer is provided, you should see a rating screen. Please rate my personal service to you. The ratings are my personal feedback,

they are not the site feedback.

Thank you for allowing me to assist you through Just Answer!

Jeremy

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Technician: Jeremy, Certified Truck/Bus Technician replied 2 years ago

If you are trying to find out if you can bypass everything and run straight to the starter, on a manual, yes you can. On automatic, no you can't. Automatic runs through the PCM for the neutral safety switch on it.

Sound like a big job with the harness on this one if you are finding more and more bad wires as you go along. Usually on a issue like that, I pull the whole dash out and order a new loom which will have all the plug ends marked.

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Customer reply replied 2 years ago
lots of broken loom and wiring on vehicle side. Thank you for your time.
Technician: Jeremy, Certified Truck/Bus Technician replied 2 years ago

Ouch. Jobs like that get pretty rough.

That diagram I posted is tight off of the Chevy website so it should match up to your truck and what you have in it.

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Technician: Jeremy, Certified Truck/Bus Technician replied 2 years ago

I see you viewed this and this is still showing as an open question due to no positive (3 stars or more) rating.

Were you not pleased with my service to you or is there a rating issue? Please let me know if you still need assistance with this, if there is a rating issue, and/or you need more time to respond.

I like to make sure all my customers are satisfied since you did pay a deposit for me to assist you, whether I’m paid by a positive rating feedback or not.

We can continue where we left off or start over if needed. Also, if you need diagrams, instructions, etc please don’t hesitate to ask.

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Jeremy
Jeremy
Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
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