Trailer System and Brake Control Failure with Codes-Help Needed...
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Junior Member
Joined: Feb 2017
Posts: 15
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Trailer System and Brake Control Failure with Codes-Help Needed...
I threw my 7x14 double axle with brakes on today to go get a cord of wood. About 10 miles into the trip I get "Left light malfunction." I pull over, check the connection-seems fine. Turn signal isn't working. I unplug, replug and all is okay-turn signal is working again. About 15 miles later I get "Trailer disconnected" then nearly immediately followed by "Trailer Connected." While the trailer is "disconnected" I lose the trailer brake control but all the running lights still work and the 7x14 trailer is still showing as active in the trailer dash display. I check and the connection is fine again. I keep getting the connected-disconnected messages over the next 30 miles but the whole time the trailer profile for my 7x14 is still showing in the trailer control section. I find this odd b/c when I don't have a trailer connected it says "no trailer connected." And the kicker: when I pinch the trailer brake controller I don't get the gain setting pop up, I get "no trailer connected" message. Even when I don't have a trailer connected and I pinch the brake controller I get the gain pop up (no green brake effort display but it shows the gain setting and let's me change it). So, I get home, uncouple the trailer and head out and it's still showing my 7x14 trailer profile as active despite the trailer is miles away. About a half hour into my trailerless trip I get "Trailer disconnected" and the dash finally reads "No active trailer."
I get home from the trailerless trip and run the codes: I get B1D09-Righthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery and B1D08-Lefthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery.
That was far longer than I expected it to be when I was thinking about posting but any insight would help. I drove it to the dealership and they confirmed it was all jacked up and made an appointment for me this week.
I get home from the trailerless trip and run the codes: I get B1D09-Righthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery and B1D08-Lefthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery.
That was far longer than I expected it to be when I was thinking about posting but any insight would help. I drove it to the dealership and they confirmed it was all jacked up and made an appointment for me this week.
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Joined: Dec 2016
Posts: 233
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Do you have any other vehicle you can hook up to the trailer to check out the trailer wiring? Sounds like a bad connection; probably a bad ground on the trailer. The crazy feedback the truck would get from a bad ground would explain all the strange readings and why the truck didn't think the trailer had brakes but still knew the trailer was plugged in.
The dealer should be able to identify if the truck is causing any of the issues, but my initial reaction would be the trailer.
The dealer should be able to identify if the truck is causing any of the issues, but my initial reaction would be the trailer.
Thread Starter
Junior Member
Joined: Feb 2017
Posts: 15
Likes: 5
Do you have any other vehicle you can hook up to the trailer to check out the trailer wiring? Sounds like a bad connection; probably a bad ground on the trailer. The crazy feedback the truck would get from a bad ground would explain all the strange readings and why the truck didn't think the trailer had brakes but still knew the trailer was plugged in.
The dealer should be able to identify if the truck is causing any of the issues, but my initial reaction would be the trailer.
The dealer should be able to identify if the truck is causing any of the issues, but my initial reaction would be the trailer.
I have no problem digging around to see where they ground the trailer and checking that connection but why is the truck still showing the trailer as connected well after I disconnected??
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Joined: Dec 2016
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A visual inspection of the connector is likely adequate to see if the trailer/vehicle connection is the problem. I would pay special attention to the ground and trailer brake pins. But a bad ground on the trailer itself could cause all kinds of strange readings to be sent to the truck.
I can't necessarily explain why the truck continued to think the trailer was connected for long after it wasn't, but it would seem like a logical safety fail-safe to me that the truck would assume a trailer is still connected and continue to output signal to keep function of the tail lights if the truck was detecting multiple faults in the trailer system. If you've dealt with grounding issues before, you know they can cause a multitude of inexplicable symptoms, so I would check the trailer wiring first since anti-corrosion and ground protections are generally not as advanced on trailers as trucks.
I had a trailer with a bad ground that blew out my reverse lights, lighted up the LH running lights when the brakes were applied, lit up the RH brake light with the running lights, and flashed everything with the RH blinker. I can imagine if I had that trailer hooked up to the more advanced trailer system on my truck, the truck would be reporting all kinds of strange things.
I can't necessarily explain why the truck continued to think the trailer was connected for long after it wasn't, but it would seem like a logical safety fail-safe to me that the truck would assume a trailer is still connected and continue to output signal to keep function of the tail lights if the truck was detecting multiple faults in the trailer system. If you've dealt with grounding issues before, you know they can cause a multitude of inexplicable symptoms, so I would check the trailer wiring first since anti-corrosion and ground protections are generally not as advanced on trailers as trucks.
I had a trailer with a bad ground that blew out my reverse lights, lighted up the LH running lights when the brakes were applied, lit up the RH brake light with the running lights, and flashed everything with the RH blinker. I can imagine if I had that trailer hooked up to the more advanced trailer system on my truck, the truck would be reporting all kinds of strange things.
Thread Starter
Junior Member
Joined: Feb 2017
Posts: 15
Likes: 5
A visual inspection of the connector is likely adequate to see if the trailer/vehicle connection is the problem. I would pay special attention to the ground and trailer brake pins. But a bad ground on the trailer itself could cause all kinds of strange readings to be sent to the truck.
I can't necessarily explain why the truck continued to think the trailer was connected for long after it wasn't, but it would seem like a logical safety fail-safe to me that the truck would assume a trailer is still connected and continue to output signal to keep function of the tail lights if the truck was detecting multiple faults in the trailer system. If you've dealt with grounding issues before, you know they can cause a multitude of inexplicable symptoms, so I would check the trailer wiring first since anti-corrosion and ground protections are generally not as advanced on trailers as trucks.
I had a trailer with a bad ground that blew out my reverse lights, lighted up the LH running lights when the brakes were applied, lit up the RH brake light with the running lights, and flashed everything with the RH blinker. I can imagine if I had that trailer hooked up to the more advanced trailer system on my truck, the truck would be reporting all kinds of strange things.
I can't necessarily explain why the truck continued to think the trailer was connected for long after it wasn't, but it would seem like a logical safety fail-safe to me that the truck would assume a trailer is still connected and continue to output signal to keep function of the tail lights if the truck was detecting multiple faults in the trailer system. If you've dealt with grounding issues before, you know they can cause a multitude of inexplicable symptoms, so I would check the trailer wiring first since anti-corrosion and ground protections are generally not as advanced on trailers as trucks.
I had a trailer with a bad ground that blew out my reverse lights, lighted up the LH running lights when the brakes were applied, lit up the RH brake light with the running lights, and flashed everything with the RH blinker. I can imagine if I had that trailer hooked up to the more advanced trailer system on my truck, the truck would be reporting all kinds of strange things.
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Joined: Aug 2019
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I threw my 7x14 double axle with brakes on today to go get a cord of wood. About 10 miles into the trip I get "Left light malfunction." I pull over, check the connection-seems fine. Turn signal isn't working. I unplug, replug and all is okay-turn signal is working again. About 15 miles later I get "Trailer disconnected" then nearly immediately followed by "Trailer Connected." While the trailer is "disconnected" I lose the trailer brake control but all the running lights still work and the 7x14 trailer is still showing as active in the trailer dash display. I check and the connection is fine again. I keep getting the connected-disconnected messages over the next 30 miles but the whole time the trailer profile for my 7x14 is still showing in the trailer control section. I find this odd b/c when I don't have a trailer connected it says "no trailer connected." And the kicker: when I pinch the trailer brake controller I don't get the gain setting pop up, I get "no trailer connected" message. Even when I don't have a trailer connected and I pinch the brake controller I get the gain pop up (no green brake effort display but it shows the gain setting and let's me change it). So, I get home, uncouple the trailer and head out and it's still showing my 7x14 trailer profile as active despite the trailer is miles away. About a half hour into my trailerless trip I get "Trailer disconnected" and the dash finally reads "No active trailer."
I get home from the trailerless trip and run the codes: I get B1D09-Righthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery and B1D08-Lefthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery.
That was far longer than I expected it to be when I was thinking about posting but any insight would help. I drove it to the dealership and they confirmed it was all jacked up and made an appointment for me this week.
I get home from the trailerless trip and run the codes: I get B1D09-Righthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery and B1D08-Lefthand Trailer Direction Indicator Circuit. Additional Fault Sympton: Short Circuit to Battery.
That was far longer than I expected it to be when I was thinking about posting but any insight would help. I drove it to the dealership and they confirmed it was all jacked up and made an appointment for me this week.
