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Old 09-21-2015, 09:13 PM   #1 (permalink)
padredw
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ITBC Quit Working Suddenly. Troubleshooting HELP?

I have read many of the post in this forum, but most of them deal with how to connect the wiring. In my case, the wiring has been working for thousands of miles, but now my brakes are not working. The conditions are exactly as several others have described: Static dashes, not moving bars. I get no electrical output at either of the plugs (bumper or in bed.) All trailer lights continue to work, but NO brakes.

This happened suddenly near the end of a 3000 mile RV trip. The Disply did come on "Check Trailer Brake Sytem," but does not come on again.

I have checked the fuses under the hood. All seem to be intact.

Can anyone suggest simple steps of trouble-shooting for a very mechanically challenged owner. My 2008 Duramax/Allison has 80,000 miles--most of it towing a 34' fifth-wheel. I had the brakes on my trailer inspected and adjusted just before this last trip. They worked until the last 150 miles.

Thanks for any help you can give.

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Old 09-21-2015, 10:18 PM   #2 (permalink)
heymccall
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Underhood 30amp fuse? The one that looks like the bottom half of a Lego man. Pink, and in the front row, IIRC.

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Old 09-23-2015, 09:07 AM   #3 (permalink)
padredw
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Thanks for the response, but I have checked all the fuses in the box under the hood. What would be the next step in trouble shooting?
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Old 09-23-2015, 12:05 PM   #4 (permalink)
heymccall
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You'll need to build an "itbc tester". A car headlamp on a 7 pin plug. In a crappy internet area, or I'd link it.
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Originally Posted by GetSome8.1HD
Its not like I said I enjoyed reading Good Housekeeping while taking a candle lit bubble bath then proceeding to using a loofah with exfoliating creams all while thinking about you . Now THAT would be creepy
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Old 09-23-2015, 12:47 PM   #5 (permalink)
padredw
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Thanks also for this. I have seen that video and may try it. But . . .

I already know that I am getting electrical output from the 7 way plug to ALL lights and NO output to the brakes. I have tried all plug outputs with a multimeter--several times with this same result.

Would the test lamp tell me anymore? I am certainly willing to try.
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Old 09-23-2015, 01:02 PM   #6 (permalink)
15Chevy2500
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Just went thru the same thing and it's not fun. My problem was in the electrical connection box under the king pin of my 5th wheel. This is where the camper plug connects to the trailer. I accidently dropped my trailer on the bed of my truck and it messed up the box itself. Little did I know it also disconnected the black power wire that feeds the brakes of the trailer. Everything else worked fine except the brakes. On mine the small black wire needed to be reconnected to the blue wire that came from the emergency cut away switch. It sounds to me like you have a disconnect somewhere in the wire that feeds power to your brakes. Is it possible that something was done when you had the brakes serviced? Maybe a wire was accidently nicked and it finally rubbed thru?
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Old 09-23-2015, 04:00 PM   #7 (permalink)
padredw
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These have all been helpful responses. My question to 15chevy2500 is: If I do not get an electrical impulse (tested by multimeter) at the truck end of the plug-in, doesn't that indicate that the trouble is in the truck and not in the trailer? This really is a question.

Now, I have been in the fuse box behind the king pin. All the fuses look good and there is no obvious disconnect.

We have just returned from a 3000 mile trip, so I'm not facing an urgent time frame. I may have to take the truck (or the trailer) to a dealer, but I like to solve as many problems on my own as I possibly can.

I recently had a display of the ENGINE LIGHT, and by connecting a OBD module found it was glow plug # 5. That was the easiest of all eight of the glow plugs for me to replace. No way would I try to replace one on the driver's side!

So, I appreciate all the replies and will try every suggestion.

Based on the above, what would be my next step?
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Old 09-23-2015, 04:12 PM   #8 (permalink)
15Chevy2500
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Padredw, if you are not getting power to the trailer brake pin on the female plug on the back of the truck then yes, the problem would be the truck. If you have already checked the fused under the hood on the drivers side of the truck and it's good then I cant help. Sorry, hope you get it fixed easily and cheaply. Let us know what you find out.
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Old 09-23-2015, 04:19 PM   #9 (permalink)
Ron Nielson
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Did you see this?

https://www.dieselplace.com/forum/76-...ml#post7668017
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Old 09-23-2015, 05:33 PM   #10 (permalink)
heymccall
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A test light or volt meter will NOT verify itbc output. A headlamp must be used. The fact that your dashes on the DIC do not change lends me to the belief that the master cylinder pressure switch is bad. Again, a homemade tester is where to start. If the sensor is bad, after changing it, the front calipers will need to be bled.

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Quote:
Originally Posted by GetSome8.1HD
Its not like I said I enjoyed reading Good Housekeeping while taking a candle lit bubble bath then proceeding to using a loofah with exfoliating creams all while thinking about you . Now THAT would be creepy
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