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I have a C15 MBN powered 2004 T800 that turns over but wont…

I have a C15...

I have a C15 MBN powered 2004 T800 that turns over but wont start

Mechanic's Assistant: What's the make/model/year of your truck? Engine type?

T800, 2004 C15 mbn

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

Trying to dianose this problem, its sat for a couple months but this is the first time its failed to start in the tr

Mechanic's Assistant: Anything else you want the truck mechanic to know before I connect you?

I believe its an electrical issue

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Answered in 2 minutes by:
6/10/2018
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
Thanks for asking your question. I will try and help you out.
Does the yellow check engine light come on when the key is turned to the on position?
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Customer reply replied 4 years ago
No it does not
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.If the yellow check engine light does not come on when the key is turned to the on position and the engine will not start, there are only 2 things that can cause this.The first and most common is the engine ECM is not getting the correct power and ground to function. The ECM should have power on pins 52, 53, and 70 of the rear most ECM connector. This is the truck side harness connector. 70 is the key switch wire. The grounds are on pins 65 and 67. You can remove the connector and check for power on these pins. If you do not have power on these pins, you most likely have a blown fuse in the electrical system. I would check all fuses first.If you do have correct power and ground to the ECM, you most likely have a failed ECM. I have seen this many times over the years. To confirm the ECM is bad, you would need to install a known good ECM on the engine or you can take the ECM to the dealer to be tested. Unfortunately the ECM cannot be repaired. Replacement is the only option. I am sorry. I wish I had better news.Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 4 years ago
I will try these first....I'm at home and don't have access to parts today..if you could tell me the position of the fuses to check in the fusebox it would be a huge help
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Many Kw trucks have fuses in the battery box. They go directly to the ecm.
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Customer reply replied 4 years ago
Thank you
Technician: Cat Man, Cat Engine Expert replied 4 years ago
You are very welcome my friend. I am happy I could help.
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
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