# Trailer brake problem



## QuadRacer041 (Sep 1, 2003)

I have an 09 3500 mason dump. this morning I got a message on my dash saying service trailer brake system. Any idea where to start? I have a digital code reader and it says no codes found. I pull my landscape trailer with this truck everyday, this morning is the first time I've seen this message.


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## basher (Nov 13, 2004)

Check the plug on the back. Could be corrosion in between the harness plug and the truck side trailer plug.


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## QuadRacer041 (Sep 1, 2003)

I will check that out.


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## SullivanSeptic (Nov 30, 2008)

Corrosion. I get it all the time. I cut my 7 pin adapter off when i installed road armor rear bumper and I get the same code. It seems to be when corrosion gets to the ground wires.


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## mcwlandscaping (Sep 8, 2005)

Do the brakes still work when this code comes up?


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## QuadRacer041 (Sep 1, 2003)

Dont see any corrosion on the plug, i usually put on some die electric grease every so often. Where afe those ground wires your talking about? Lights work but no brakes. When i use the plus and minus buttons or the slider on the controller i dont feel the brakes working.


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## SullivanSeptic (Nov 30, 2008)

My corrosion was in the inside of plug where can't see it. I had to split open plug before I found it. Your best bet is to get a buddy with a truck and hook your trailer to his and see if brakes work. Then try hooking your truck to another trailer. Because it could be the trailer wiring. But most like its your 7 pin. The ground wire I'm talking about is actually on the 7 pin. Again, you might need to split it open to see.


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## QuadRacer041 (Sep 1, 2003)

I unplugged the hareness from the back on the 7 pin that is mounted to the back of the truck bumper and the code still shows up. Wouldnt that eliminate the 7 pin plug as the problem?


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## SullivanSeptic (Nov 30, 2008)

Is the code still happening when not hooked to trailer? Or only when plugged in?


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## QuadRacer041 (Sep 1, 2003)

Yes still happens even when not hooked up, I actually tried the truck connected to a different trailer and same issue. As i said even with the factory harness not plugged into the 7 pin plug the message is still there. Under the hood i did find a blown fuse, 15a the schematic shows that as being "seo b1" didn't fix the problem though, what is that for?


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## mcwlandscaping (Sep 8, 2005)

Any associated fuses with the built in brake controller that could be blown?


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## basher (Nov 13, 2004)

This is an internal issue with in the truck. search down the frame ground and clean/tighten it if you have already cleaned the corrosion out of both of the rear trailer plugs.

Have you tried a load tester (teckonsha test box or equivalent) to see if the brake control is functioning?


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## QuadRacer041 (Sep 1, 2003)

basher;1481525 said:


> This is an internal issue with in the truck. search down the frame ground and clean/tighten it if you have already cleaned the corrosion out of both of the rear trailer plugs.
> 
> Have you tried a load tester (teckonsha test box or equivalent) to see if the brake control is functioning?


Are there any fuses that could be blown? Where are they located? 
How do I load test to see if it is working? Any idea where the ground is?


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## basher (Nov 13, 2004)

The controller needs to read a magnet to operate. either a teckonsha test box or a plug with a magnet wired to the brake (blue) and Ground (white) and sitting on a metal grounded surface of the truck.

one heavy ground is normally screwed into the rear frame crossmember or passenger side frame rail.

This could also be a corroded/bare spot/pinch in the brake feed (blue) wire. 

Have you added any additional wiring, spliced into the ground or blue wire for reason or added a in bed plug for a 5th wheel or Gooseneck?


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## QuadRacer041 (Sep 1, 2003)

Ok, I will check the ground and blue wire tomorrow.
No I have not tapped into either the ground or the blue wire for anything. Everything was working fine on Friday, Monday I got in the truck to go to work and thats when the problem started.


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## cet (Oct 2, 2004)

Do you have a seperate ground on your trailer or does it ground through the hitch. Mine just through the same code on Sunday and it was the grounding through the hitch working and not working. When the truck was pulling the trailer I had no ground but when I slowed down and the trailer started pushing the truck everything worked fine.


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## QuadRacer041 (Sep 1, 2003)

cet;1481558 said:


> Do you have a seperate ground on your trailer or does it ground through the hitch. Mine just through the same code on Sunday and it was the grounding through the hitch working and not working. When the truck was pulling the trailer I had no ground but when I slowed down and the trailer started pushing the truck everything worked fine.


I still get the code even when the trailer is disconnected.


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## basher (Nov 13, 2004)

Use your trailer has a test box. First using another truck assure the trailer is correct. Then see if your brake control will activate the trailer brakes using the manual (turn them up all the way, it makes it easier to tell) activation. if they work try a rolling test (again Full power from the BC) does it activate with the pedal. This will tell you is the controller is operating. If the controller is not operating you need to take it to a Ford dealer or replace with an aftermarket nod:)


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## QuadRacer041 (Sep 1, 2003)

The truck is a chevy, why take it to ford? As i stated earler i tried connecting to another trailer with the same results. Also the code appears even if no trailer is connected. Also as stated earlier raise or lowering the gain as well as sliding the manual slider over has no affect.


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## basher (Nov 13, 2004)

Sorry Ford has the same issue, same solutions. Have you checked to see if you have the gooseneck harness behind the cab? Could be an issue there (rubbed wire, etc.) 

If the controller is getting power, but not producing it I would guess it is a controller issue. Chevy controllers are VERY sensitive and will tolerate NO additions. Many Chevy dealerships know little about them and tend to use replacement as the first option although sometimes they (the Truck)forget they have a brake controller and you have to flash the computer.


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## cet (Oct 2, 2004)

I'm grasping at straws but have you checked the fuses. You know there are different fuses for the trailer wiring located in the fuse box under the hood.


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## QuadRacer041 (Sep 1, 2003)

Ok, checking the wires going into the controller. There are 6 wires, the blue wire has power going into the controller but wheb i hold tbe manual slider all the way over none of the other wires have power. Same thing when i hold the brake pedal down.


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## basher (Nov 13, 2004)

QuadRacer041;1481627 said:


> Ok, checking the wires going into the controller. There are 6 wires, the blue wire has power going into the controller .


OK blue is the power feed to the brakes. It should not have amperage unless the controller is engaged. What are you using to test? You could just be getting a continuity signial.

OK remember the controller is inert until it reads continuity to a set of magnets so you need to test it with a working trailer/test box plugged in and the switch key in the on position.


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## QuadRacer041 (Sep 1, 2003)

Ok, how is the blue wire having power if that supplies power to the brakes. Im talking about the harness that actually plugs into the controller itself. If that supplies power to the brakes how does it have power without another wire going into the controller giving it power?
The way im testing is key in run position, trailer connected, manually sliding over the slider on the controller and having a test light to tell me is im getting power to each wire.


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## basher (Nov 13, 2004)

QuadRacer041;1481645 said:


> Ok, how is the blue wire having power if that supplies power to the brakes. Im talking about the harness that actually plugs into the controller itself. If that supplies power to the brakes how does it have power without another wire going into the controller giving it power?
> The way im testing is key in run position, trailer connected, manually sliding over the slider on the controller and having a test light to tell me is im getting power to each wire.


how many volts from the blue wire? You are talking about the dark blue wire. Correct?


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## brad96z28 (Aug 21, 2005)

Its usually the pressure switch on these. Its quite common. Also any kind of moisture in the trailer plug will do it also.


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## QuadRacer041 (Sep 1, 2003)

basher;1481658 said:


> how many volts from the blue wire? You are talking about the dark blue wire. Correct?


yes, i will check that today.


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## QuadRacer041 (Sep 1, 2003)

brad96z28;1481718 said:


> Its usually the pressure switch on these. Its quite common. Also any kind of moisture in the trailer plug will do it also.


where is the pressure switch located


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## affekonig (Aug 5, 2008)

Condition/Concern:

Some vehicles may exhibit setting DTC B3894 Symptom 5A-Stop lamp Switch Circuit Plausibility. Many Stop Lamp Switches have been returned to the WPC for inspection and duplication on test vehicles; however, failure of these switches was not confirmed. We believe that the code was being set by a wiring/terminal issue at the brake switch.

Recommendation/Instructions:

Prior to replacing any switches, the terminals at the brake switch should be inspected. This condition may be caused by a buildup of non-conductive insulating oxidized debris known as fretting corrosion, occurring between two electrical contact surfaces of the connection or connector. This may be caused by any of the following conditions:

• Vibration 

• Thermal cycling 

• Poor connection/terminal retention 

• Micro motion 

• A connector, component or wiring harness not properly secured resulting in movement 

On low current signal circuits this condition may cause high resistance, resulting in intermittent connections.


Note: Fretting corrosion looks like little dark smudges on electrical terminals and appear where the actual electrical contact is being made. In less severe cases it may be unable to be seen or identified without the use of a magnifying glass.

Important: DO NOT apply an excessive amount of dielectric lubricant to the connector as shown, as hydro lock may result when attempting to mate the connector. Use ONLY a clean nylon brush that is dedicated to the repair of the conditions in this bulletin.

1. With a one inch nylon bristle brush, apply dielectric lubricant to both the brake switch side and the harness side of the affected connector. 

2. Reconnect the affected connector and wipe away any excess lubricant that may be present.


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## affekonig (Aug 5, 2008)

Condition/Concern:

Some customers may comment of a Service Trailer Brake message on the DIC and one or more of the following DTC's: C1115, C1116, C1117, C1118. This concern may be very intermittent and can occur with or without a trailer connected to the truck. During a recent warranty review of returned Trailer Brake Control Switches all switches were found to be NTF (No Trouble Found).

Recommendation/Instructions:

Before replacing any parts inspect the wiring to the switch near the parking brake pedal assembly.

Several reports of the wiring being chaffed in this area have been received. Repair any circuits that have been chaffed and reposition/protect the wiring so the concern does not reoccur.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


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## QuadRacer041 (Sep 1, 2003)

Truck is at the dealer, just dont have the time to do all the testing to find the problem. Truck is still under warranty, I will let you know what the problem was when I get it back.


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## QuadRacer041 (Sep 1, 2003)

Ok, picked up truck from dealer. No message on the way home, will hook up trailer and check trailer brakes tomorrow morning. This is what was in the comments said on my reciept:
Check trouble codes found code c0561 serial data check ebcm codes c0131 master cylinder presure sensor intermittent. Test at ebcm, tested ok. tested all terminals, road test, light came back on. retest voltage and ground ok. Signal from sensor open, test sensor, open circut. Remove and replace brake cylinder presure sensor, clean code, road test concern ok.
Part # was 15838718


I have a couple of questions: Why didnt I see any of these codes when I tested with my code reader? What does signal from sensor open mean? Test sensor open circut??????
Can anyone tell me where that sensor is located? Is it on the master cylinder?


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## brad96z28 (Aug 21, 2005)

I would bet you are using a pos scanner.You get what you pay for. A walmart / autozone/pepboy scan tool Is not a reliable tool. Most cars today can have 40 or more modules that can set codes.I would assume the scanner u have reads only in generic global.Most of those types can only pull codes from the ecm/pcm. Id say 75% of dealers no longer even use scan tools anymore, most everything dealer level is lap top.Like I said the pressure sensors are very common on these. The sensor open means it shows no resistance with a meter meanin it is open circut. It should measure resistance with a meter.Yes the sensor is on the master cyl.


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## brad96z28 (Aug 21, 2005)

Also this problem takes about 5 min tops to figure out with a good scanner., even without a code. Step on the brake and watch the pressure reading on the tool no change u go rite to the switch and test it.


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## snowymassbowtie (Sep 22, 2013)

Im getting the service trailer brake sytem on the dic. The truck is supposed to have provisions for a
5th wheel that you can wire a 7 pin plug in the bed of the truck, I think its above the gas tank. I was not able to find it.and has never had a plug wired in the bed so the wires should be dead ended ? The bolts for the tank straps are pretty crusty and I don't want another problem breaking the bolts to look up there.I know I can lift the bed but I would rather not take it off if I don't have to,yet anyways. I have pulled pushed, wiggled the harness as much as I can and nothing changes. From out of the controller at full 10.0 gain. I get 5.1 volts from the controller from the blue wire that I believe is the one that goes from the controller to the brake module. Im getting 5.1 volts into the brake mo volt wire to that blue wire I get 12 volts at the plug. Im thinking its the relay ? This all started after I brought it to a body shop.They removed the rear bumper but when they put it back on they didn't connect the connector to the 7 pin. It was in march when I plowed etc.. After a week or so I got the messge on the d.i.c. I found the disconnected plug and it was wet. I took it back to the shop,they replaced the 7 pin with an aftermarket but the error came right back on. They said it must be something else and then said to take it to the dealer on my dime. Im thinking that might have killed the relay. I have checked all the fuses and they were all good. For $30.00 so I ordered. If any one has any ideas please let me know. I don't have money to bring it to a dealer and I have read that some dealers just throw parts at it to see if it fixes it. I have brake and all testing was done with the key on. Thanks for taking the time to read this. The truck is a 2009 2500 hd gas


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## cwren2472 (Aug 15, 2014)

snowymassbowtie said:


> I have pulled pushed, wiggled the harness as much as I can and nothing changes. From out of the controller at full 10.0 gain. I get 5.1 volts from the controller from the blue wire that I believe is the one that goes from the controller to the brake module. Im getting 5.1 volts into the brake mo volt wire to that blue wire I get 12 volts at the plug. Im thinking its the relay ? This all started after I brought it to a body shop.They removed the rear bumper but when they put it back on they didn't connect the connector to the 7 pin. It was in march when I plowed etc.. After a week or so I got the messge on the d.i.c. I found the disconnected plug and it was wet. I took it back to the shop,they replaced the 7 pin with an aftermarket but the error came right back on. They said it must be something else and then said to take it to the dealer on my dime. Im thinking that might have killed the relay. I have checked all the fuses and they were all good.


There IS a relay, but it only brings power to the ITBC, it is not responsible for output voltage.

As far as the 5.1 volts, on an older GM with the ITBC, the controller is inertia activated and, even with the controller cranked to the max and the slide depressed, it will not put 12 volts to the brakes if it does not sense motion, so you can not test it that way.

The truck computer is very sensitive to bad connections - any movement in the plug is enough to change the voltage and throw the error code. Did they mount the trailer plug differently after changing the bumper? If so, the trailer cord may be pulling on it differently. Also, did they just snap a new aftermarket plug onto the factory OEM connector or did they cut off the OEM connector entirely and hardwire the new plug? If the OEM connector is still there, it very likely may be corroded.

Also, I can't speak for dealers near you, but I can't say I've found a dealer yet that can diagnose ANYTHING to do with the factory trailer equipment, regardless of how small an issue.


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## FredG (Oct 15, 2012)

You definitely don't want to bring it to the Dealer, older GM they will say it needs $2500.00 worth of work. FWIW if you start your own post on your problem you will get more action, Some Members will graze over old threads. Cwren is just a nice Guy lol. Good Luck


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## GetMore (Mar 19, 2005)

I believe the provision for a 5th wheel harness places a connector similar to the one on your bumper, but high inside the bed, near the left side of the tailgate. It should not be hidden somewhere.

I had this same thing pop up on my truck, and it solved itself, which means it is ready to do it again next time I need to trailer something. 
The funny thing is that I had a friend who is a mechanic service the truck, and that is when the problem occurred. It was a few days after he returned the truck to me that it went away again.

The best advice was given a few posts up. Get the code and Google it, and you will find the same advice. 
The module looks for a certain voltage when it does it's self-test. More or less and it will throw a code. This is why you can get the message without a trailer connected. They dealer can also reprogram the module, which I believe allows a wider voltage range before tripping the code. If you have a good relationship with the dealer, or it is under warranty that is the way to go.


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