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1999 freightliner fl60 with cat 3126. Will not start. Wait…

Customer Question
1999 freightliner fl60 with...

1999 freightliner fl60 with cat 3126. Will not start. Wait to start light not coming on and scanner will not communicate with ecm. Unplugged wiring harness going to sensors to rule out a shorted sensor. Still nothing. Next step I was going to check fuse panel but have no diagram.

Mechanic's Assistant: How long have you had trouble with the light?

Haven’t had any trouble with it. I worked on this truck once before and if the light doesn’t come on then it isn’t powering up the ecm

Mechanic's Assistant: What's the make/model of your 1999 truck?

1999 freightliner fl60 with cat 3126. Will not start. Wait to start light not coming on and scanner will not communicate with ecm. Unplugged wiring harness going to sensors to rule out a shorted sensor. Still nothing. Next step I was going to check fuse panel but have no diagram.

Mechanic's Assistant: Is there anything else the freightliner Mechanic should know before I connect you? Rest assured that they'll be able to help you.

It was running and customer shut it off and now it won’t start and I have no communication with ecm. I can communicate with abs module

Submitted: 11 months ago.Category: Medium and Heavy Trucks
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Answered in 26 minutes by:
8/24/2021
Technician: Cat Man, Cat Engine Expert replied 11 months 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 you question. I will try and help you out.

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 11 months ago
I'll check it tomorrow.
Technician: Cat Man, Cat Engine Expert replied 11 months ago

10-4

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Customer reply replied 11 months ago
Thanks for your help
Technician: Cat Man, Cat Engine Expert replied 11 months ago

You are very welcome my friend. I am happy to help.

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Customer reply replied 11 months ago
Do u have a diagram or pin out of connector. I'm back on site to check wiring
Customer reply replied 11 months ago
Not needed
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