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Old 11-11-2015, 02:02 PM   #1 (permalink)
Bigwooo
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Geez....one more trailer brake issue

Occasionally while driving my truck without the trailer I'd get a "Service Trailer Brake" warning when going over a speed bump. Never had the warning while towing. Then after a while the truck wouldn't give the "Trailer Connected" message on the dash when I connected the trailer to the truck, and the trailer brakes stopped working. I'd disconnect then re-connect the trailer connector and the trailer brakes would work until I turned the ignition off again. The disconnect/connect thing worked for several stops, but eventually the trailer brakes failed completely.

I assumed the problem was in the wiring so I replaced both the truck and trailer connectors along with the wiring harnesses. That didn't fix the problem.

After reading several of the threads I made a light bulb tester with a 12v bulb that had 2.5 ohms of resistance (I think it was a brake light), hooked it up to the blue and white wires on the truck output and it still didn't give the "trailer connected" message, or any bars on the gain when the pedal was depressed. No output whatsoever.

I have a code reader and there's no error codes in memory.

I measured the resistance between the white and blue on the trailer and it's 4.5 ohms, so I assume the wiring isn't cut or shorted on the trailer side.

Just to be sure, I found another trailer with brakes and same electrical connectors. Still didn't recognize the trailer, or actuate the brakes.

After all this I assume the problem is on the truck side. I looked under the dash over the brake pedal to try and find the controller, but couldn't recognize what/where it was. I wanted to check for maybe a loose connector.

I'm in Mexico and would like to try and fix this myself, or else I'm going to have to tow the trailer 850 miles when I head back to the U.S. without trailer brakes. It's only 19 foot travel trailer, so it's doable, but I'd rather not. It'll still be a long slow trip.

Where should I go from here? I'm not a complete mechanical moron, but I'm not that familiar with auto mechanics either. With a little online instruction is this something I should try to tackle on my own, or is it just too complicated from this point for a novice? There's no chance of finding someone here that can do the repairs. Thanks!

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1997 Ford crew cab 4WD, long bed, service body, custom front/rear bumpers, HD front/rear springs, 2 inch lift 285/75/16 BF all terrains, Rancho 9000's, Racor 500, Lance 8' Camper. Used to search for surf on remote beaches of Baja California. Never left me stranded. Sold in '08. Was sad to say goodbye to such a good reliable truck.

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Old 11-11-2015, 03:14 PM   #2 (permalink)
Ron Nielson
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Check ITBC fuse (#21 probably), Check the CHMSL fuse (#49 probably), Stud 1 (#66 )fuse, stud 2 (#61) fuse. Don't just look at them, make sure they pass electricity with a tester.
  • The Trailer brake connector should measure less than 2 ohms (I believe you said 4.5 which is too high) of resistance between pins A & B of the trailer side connector. Note - a minimum of one fully functioning axle of brakes is required for the TBCM system to function correctly.
You must have a functioning ABS system. If ABS light on dash is illuminated while driving, address the ABS problem. Your brake pressure sensor on the master cylinder may not be working; your ITBC relay or ITBC module (new modules require dealer programming) on the frame near drivers side may may be defective; ITBC switch on the dash may be defective. Brake light switch may be defective. If you have camper (not trailer) wiring, make sure the blunt cut wires near frame at front of bed are not grounding in any way (wrap in plastic after coating with dielectric grease -if available).

Very frustrating and time consuming to assess, diagnose and fix this problem. (I fixed mine, but not at all sure what I did to make the fix.) There are many possibilities for problems. Look on internet for article by Lenn Todd describing the ITBC system. Good basic information. Good luck to you.

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Old 11-11-2015, 05:49 PM   #3 (permalink)
Bigwooo
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Thanks Ron. I'll check the fuses you suggest and go through the trailer thoroughly just in case there's a problem there, but I'm pretty sure it's the truck. It sounds like any further troubleshooting is waaay over my head, but I'll read the article and see.... Looks like it's probably going to be a long trip North without trailer brakes though...
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2008 Duramax crew cab, 4WD, long bed. Line-X'd the bed/wheel wells, 265/75/16 BFG AT's, Torklift frame mount camper tie downs, lubrication specialist secondary fuel filter, Buckstop bumper, Piaa off road lights, Duraflaps rear/ DeeZee running board front, air ride air bags, Rancho 9000XL shocks (Blown in less than 15,000 miles), changed to Bilstein 5100's.

1997 Ford crew cab 4WD, long bed, service body, custom front/rear bumpers, HD front/rear springs, 2 inch lift 285/75/16 BF all terrains, Rancho 9000's, Racor 500, Lance 8' Camper. Used to search for surf on remote beaches of Baja California. Never left me stranded. Sold in '08. Was sad to say goodbye to such a good reliable truck.

1994 Ford F250 Diesel Sold

1972 Ford F250 Gasser-RIP
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Old 11-11-2015, 07:32 PM   #4 (permalink)
heymccall
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Without trailer, and getting a message, the UY2 harness is compromised at its terminus.
The 4.5 ohm is too high. That tells me that only 1 magnet is connected, or the trailer wiring is compromised. Each magnet is 4 ohm. Therefore a single axle should be 2 ohm, and a tandem axle should be nearly 1 ohm.

As for the tester, a regular old sealed beam headlamp is what I use. A stoplamp or turn signal bulb will NOT work.
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Old 11-11-2015, 07:46 PM   #5 (permalink)
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Under rear of truck, near spare tire is a block where harness connects to truck side connector, and wires from front come in. look there for dirty and or loose connections. you can also check with meter at the camper plug wires mentioned above.
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Old 11-11-2015, 08:15 PM   #6 (permalink)
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Quote:
Originally Posted by TiredFarmer View Post
Under rear of truck, near spare tire is a block where harness connects to truck side connector, and wires from front come in. look there for dirty and or loose connections. you can also check with meter at the camper plug wires mentioned above.
Not quite. The 7pin (8 wire) trailer harness is continuous from underhood to the 7 pin plug. IF you have the UY2 option (look on glove box door label), that 7pin connector doesn't go straight to the trailer plug in the bumper. It will plug into a fifth wheel harness that goes to front of the bed and the bumper plug, but again, only if the UY2 option is present.
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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 11-11-2015, 08:18 PM   #7 (permalink)
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Quote:
Originally Posted by heymccall View Post
Not quite. The 7pin (8 wire) trailer harness is continuous from underhood to the 7 pin plug. IF you have the UY2 option (look on glove box door label), that 7pin connector doesn't go straight to the trailer plug in the bumper. It will plug into a fifth wheel harness that goes to front of the bed and the bumper plug, but again, only if the UY2 option is present.
Ok, thanks Brian. Guess all mine have been UY2's and I just assumed they were all like that.
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Old 11-11-2015, 11:05 PM   #8 (permalink)
heymccall
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And, the UY2 harness is a Tee with the long leg being blunt cut and bundled under the filler neck, and the top of the Tee has a male and female 7 pin connector, right at the bumper socket. The UY2 harness can be isolated by plugging the 7 pin plug directly into the bumper plug, and leaving the UY2 Tee harness offline.

The junction block for the rear lighting has never, and still doesn't, included the trailer harness wiring, on any year of gm truck. All trailer wiring in gm trucks is direct from underhood, to the rear bumper, with no connections in between.
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'13 Hyundai Genesis Coupe handshaker
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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
Member #21 of the OiO association

Last edited by heymccall; 11-11-2015 at 11:09 PM.
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Old 11-12-2015, 01:45 PM   #9 (permalink)
rdminter
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I am so glad I went wireless for my controller, no worries about connection problems.
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Old 11-12-2015, 06:17 PM   #10 (permalink)
heymccall
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I don't see "connection" problems. I see UY2 equipped trucks that don't get a bed socket have issues with the blunt ended bed connection wires, and shtty (shoddy) trailer wiring.

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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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