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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 7392
Experience:  Owner at DJ Wilson
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I've got a truck with only one brake light illuminating.

Customer Question

I've got a truck with only one brake light illuminating. Both blinkers work fine. Replaced bulbs, and switch. What are we missing. Truck VIN-1XPHD49X4CD158304
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Heavy Truck Mechanic I'm going to connect you with knows all the tricks and shortcuts.
Customer: Ok
JA: Are you fixing your truck yourself? What have you tried so far?
Customer: yes. Replaced fixtures with LED ones, traced wiring back to harness out of cab. We get blinker signal but no brake signal for the right blinker/brake wire. Left side works like it should. Replaced the blinker assembly with a new one. Same thing.
JA: Anything else you want the truck mechanic to know before I connect you?
Customer: A harness schematic for this could be helpful
Submitted: 7 months ago.
Category: Medium and Heavy Trucks
Customer: replied 7 months ago.
Sorry it's a 2012 Peterbilt 386 with a Cummins ISX 15
Expert:  Daniel Wilson replied 7 months ago.
Hi my name is***** will be glad to help. I'm not sure if you are aware but this truck has Multiplexed electrical meaning the lighting circuits are programmed into electronic modules. So there are smart switches programmed into the inputs and then the outputs go out to the lights. Therefore this is not just basic or standard wiring of switches relays and lights with a ground. This actually involves computer software and programming as well. Sometimes the LED lights will throw off the module if the polarity is not correct on the bulbs and then in other cases the resistance from the LED style lights sometimes will throw off the module to shut down the circuit thinking there is a short or problem in the electrical because of the different resistance from the LEDs. This is another thing to look into for a potential cause of your problem. Check for these and let me know the results as we can follow up as needed on here.
Customer: replied 7 months ago.
How is that answer $41? Problem resolved earlier this morning.
Expert:  Daniel Wilson replied 7 months ago.

Professionals have nothing to do with billing. We are users of the site like yourself. You need to reach out to customer service for that. I log in and see what is on the board for questions I can help with along with any other professionals. Seems maybe no one was logged in at the time of your post familiar with your question. We only get credit for our time on positive feedback or accepted answers.

Customer: replied 7 months ago.
Thanks for the info Daniel.