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Veteran
Posts: 236
Location: Little town in Pa | My husband and I have been trouble shooting our trailer brakes for 2 days. He has taken each brake apart, cleaned and re greased all bearing, check the brake pads which are all reading about 5/32 and adjusted the brakes so they drag slightly when the trailer is jacked up. While the trailer is still jacked up, the tires will stop spinning when the brake controller is activated. But when you are coasting on a flat black top surface you can not stop the trailer when maxing out the hand control on the brake controller. The trailer brakes are not strong enough. My specific question is, on the plug on the truck, should the brake pin always have a pulsing voltage reading even when the brakes are not being used? Or do you have any other suggestions as to why the brakes are not strong enough? |
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Expert
Posts: 3853
Location: Vermont | What you can do is test the brake controller with a multimeter, with the vehicle sitting still. You should get a constant 12 volts on the red wire when you step on the brakes and no voltage when not stepping on the brakes. If the voltage jumps up and down with the brake pressed, you may have a bad connection on the red wire that will need to be fixed.
If you find that the red wire is showing the correct voltage, test the blue wire going out of the brake controller. I it shows the correct voltage going out and does not go up and down (pulse) then you can move on for further testing. If it does not show voltage or pulses then there is something wrong with the internal circuitry and the brake controller will need to be replaced.
If the red and blue wires are both correct, move on to testing the pins at the 7-Way while someone sits in the truck and applies the brake. If voltage is going thorough as it should, then you know the problem must be on the trailer side. If it is not coming through like it should then you know there is a wiring issue somewhere between the connector and the brake controller and you will have to track it down. |
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Expert
Posts: 5870
Location: western PA | You should not have any voltage when the brakes are not being used. Also check to see if a full 12v is available to the brakes when the controller is fully activated. If it isn't, check the voltage at the truck's plug and then the brakes assy to see if there is a difference. If there is a difference, check the plug and trailer wiring for a bad connection. If the brakes are set so that they drag, they will eventually heat up when rotated and become inoperative when you need them. They should not rest against the drums when not in use. If the plug is older and dirty, lubricate the pins with some dielectric grease and reinsert the plug several times. |
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Veteran
Posts: 236
Location: Little town in Pa | Paul and Gard,Just to be clear, when the key is turned on in the truck and the built in internal brake controller is not being touched, should I get a pulsing voltage on my multimeter going between the neutral pin and the brake pin on the truck 7 way plug? |
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Veteran
Posts: 259
Location: Topeka Ks | Ncatanz you should not be seeing a pulse as Paul said. I would take the time to remove and clean the body grounds on the truck and then retest the controller. Just keep in mind most problems are caused by bad grounds. |
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Veteran
Posts: 236
Location: Little town in Pa | I have seen a couple posts on GMC sites that say the brake pin will have a pulsing voltage as the truck constantly looks for an attached trailer. One nice way to trouble shoot this in at the junction box near the emergency brake away switch under the gooseneck. All wires were exposed and connected under a screw terminal. Nice way to trouble shoot different scenarios. I did tighten them all and clean the plug and receptacle till they were bright brass again. I am going for another test down the driveway today. |
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Expert
Posts: 3853
Location: Vermont | Originally written by Ncatanz on 2015-08-07 3:50 AM
Paul and Gard,Just to be clear, when the key is turned on in the truck and the built in internal brake controller is not being touched, should I get a pulsing voltage on my multimeter going between the neutral pin and the brake pin on the truck 7 way plug?
No |
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Member
Posts: 17
Location: Southern Minnesota | I was having the same problem with my 08 Chevy 3500. My local mechanic was able to find a GM notification that said you needed to program your controlller each time you plugged in a trailer. You do this by going approximately 20-25 mph and use your hand control to activate the brake. Since I started doing this my trailer brakes work great. |
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Expert
Posts: 3853
Location: Vermont | Originally written by genebob56 on 2015-08-10 8:31 AM
I was having the same problem with my 08 Chevy 3500. My local mechanic was able to find a GM notification that said you needed to program your controlller each time you plugged in a trailer. You do this by going approximately 20-25 mph and use your hand control to activate the brake. Since I started doing this my trailer brakes work great.
HUH?...many trailer brake issues with GMC Trucks have to do with a bad front wheel speed sensor...computer uses the wheel speed to calculate speeds for the trailer brake system/brake bias etc. |
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Expert
Posts: 3853
Location: Vermont | Originally written by genebob56 on 2015-08-10 8:31 AM
I was having the same problem with my 08 Chevy 3500. My local mechanic was able to find a GM notification that said you needed to program your controlller each time you plugged in a trailer. You do this by going approximately 20-25 mph and use your hand control to activate the brake. Since I started doing this my trailer brakes work great. Bulletin No.: 09-05-22-004Date: November 05, 2009Subject: No "Trailer Connected" Message on Driver Information Center (DIC) at Startup When Trailer is Connected (Reprogram ITBCM)Models:2007-2008 Chevrolet Silverado2007-2008 GMC SierraEquipped with Integrated Trailer Brake (RPO JL1) Condition:Some customers may comment that when they connect their trailer, with the engine off, and after they start the engine, the Trailer Connected message is not displayed on the DIC. With the engine running, if the trailer connector is cycled, the vehicle will detect the trailer and display Trailer Connected. This concern should only affect trailers equipped with trailer brakes on a single axle.Cause: The trailer brake control system is only compatible with trailers equipped with electric trailer brakes. The system will not work or detect trailers equipped with any other types of brakes such as surge, air or electric-over-hydraulic trailer brake systems. When a trailer is connected, the Trailer Brake Control Module (TBCM) performs a test to determine if the trailer is equipped with electric trailer brakes. If the trailer wiring or electric trailer brake magnets have additional resistance (caused by poor connections, corrosion, improper splices, etc.), the TBCM may not be able to detect the trailer.Correction: A revised calibration has been developed to address these issues. Reprogram the Integrated Trailer Brake Control Module (ITBCM) with updated calibration files using the TIS2WEB Service Programming System (SPS) application. Refer to SI and Service Programming System (SPS) documentation for programming instructions, if required. Refer to Trailer Brake Control Module Programming and Setup in SI. |
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Expert
Posts: 3853
Location: Vermont | Originally written by genebob56 on 2015-08-10 8:31 AM
I was having the same problem with my 08 Chevy 3500. My local mechanic was able to find a GM notification that said you needed to program your controlller each time you plugged in a trailer. You do this by going approximately 20-25 mph and use your hand control to activate the brake. Since I started doing this my trailer brakes work great. http://www.dieselplace.com/forum/76-speciality-forums/222-towing/456202-re-map-integrated-brake-controler.html |
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Veteran
Posts: 236
Location: Little town in Pa | I just wanted to give an update on my brakes. First of all I do believe that my GMC 3500 does send out a pulsing voltage while it constantly searches for the electric brakes on a trailer when none is attached. And it turns out the problem for my weak brakes were caused by old and pitted brake magnets. Replaced them at $24 a piece plug our labor and we know have nice strong brakes. |
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Expert
Posts: 3853
Location: Vermont | Thanks for the follow up |
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Expert
Posts: 5870
Location: western PA | The pulsing from the controller is for it to identify if a trailer is attached to the towing vehicle. A short measured pulse is sent out and identified if it returns. This resistance tells the truck, that an additional closed circuit is attached. The pulse is not strong enough or actually used to activate the brakes on the trailer. This will be a larger voltage that will energise the electrical brakes' magnets. |
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