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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4291
Experience:  Owner at DJ Wilson
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I have a 2013 Freightliner Coronado, the passenger high beam

Customer Question

I have a 2013 Freightliner Coronado, the passenger high beam will not work. I have the truck on and the only high beam that works is the driver side, all lights work by the way except the passenger high beam. Even with new terminals it won't do nothing, I tried even putting the bare wires on a bulb and nothing either.
Submitted: 1 month ago.
Category: Medium and Heavy Trucks
Expert:  Daniel Wilson replied 1 month ago.

Hi my name is***** will be glad to try to help. These trucks are multiplexed wiring and the lighting circuits are programmed into the the chassis and lighting modules. Check the wiring harness and connector pins thoroughly for open circuits or damaged wires between the firewall connector and headlight and if okay between the module, headlight switch ,relays and firewall connector. If okay the next step is to have it plugged into the dealer diagnostic software and reflash/reprogram the software and check for a possible faulty module or switch. Check for chassis module fault codes. Let me know

Customer: replied 1 month ago.
I didn't understand anything, please step by step not all at once. It's obviously not the switch in the cab because the driver high beam works. I didn't understand your first sentence either. Chassis module?
Customer: replied 1 month ago.
I'm not very mechanic savvy, so light on the words please. I know what's what, but not like you described it.
Expert:  Daniel Wilson replied 1 month ago.

These trucks have multiple computer modules that control different things. Your lights and switches are all programmed into the chassis module. There is an engine computer ECM, Transmission computer TCM, and also chassis computer SAM module that the lighting circuits and other circuits for the chassis are programmed. Freightliner has exclusive rights on the diagnostic software and program to plug in an test and communicate with the chassis modules. So inspect the wiring and connector pins, bulb, etc. Beyond that you are at the mercy of the dealer.

Expert:  Daniel Wilson replied 1 month ago.

The lighting circuits on these trucks are not basic lighting circuits. They are all run through a computer.

Customer: replied 1 month ago.
how do I check the wiring besides just looking at it and everything else before going to the dealer? Because the high beam just went out a few days ago.
Expert:  Daniel Wilson replied 1 month ago.

Beyond a visual inspection of the wiring and connector pins you would need to test continuity of the wire between one end to the other end using an OHM meter. Close to 0 OHMS is a good wire.

Customer: replied 1 month ago.
What if it's the ground wire that's damaged, do I test that one the same way?
Expert:  Daniel Wilson replied 1 month ago.

Test the wire itself one end to the other yes. To then check if it is getting good ground touch one test meter lead to the wire and the other to a chassis ground and close to 0 Ohms is good

Customer: replied 1 month ago.
I'll try that today.
Expert:  Daniel Wilson replied 1 month ago.

Sounds good. Pleasure to help

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