2021 GMC Check Trail Signal lamps message with No trailer connected.

[Randy Platz]

Hello everyone.
I have a 2021 GMC 2500HD Duramax AT4. New Years eve treaded my truck to a touchless car wash. Drove home and parked in the garage (where it always parks) It sat until Monday. Upon start up in came up with a 3 messages, Check Trailer Right turn lamp, than Check Trailer Left turn lamp, then check Trail brake lamps. However there is no trailer connected. I thought maybe water in the 7 pin plug. Nope clear and dry, just a little dielectric. Check the trucks turn signals and they blink very fast light a burned out bulb. Checked all the fuses, all good. Checked under the truck and all connection look good. Thinking is the trailer lamp lighting control module. Though of going to the dealer, but of course the truck just turned 38,000.
Has anyone else ran into this? I did search online and found 1 You-tube video where a guy cut one open all corroded.
I do live in Wisconsin and land of salt. When the truck was new I had the under side coated with rubberized rust proofing.

 

[GMCustomerService]

On 1/21/2023 at 2:56 PM, Randy Platz said:

Hello everyone.
I have a 2021 GMC 2500HD Duramax AT4. New Years eve treaded my truck to a touchless car wash. Drove home and parked in the garage (where it always parks) It sat until Monday. Upon start up in came up with a 3 messages, Check Trailer Right turn lamp, than Check Trailer Left turn lamp, then check Trail brake lamps. However there is no trailer connected. I thought maybe water in the 7 pin plug. Nope clear and dry, just a little dielectric. Check the trucks turn signals and they blink very fast light a burned out bulb. Checked all the fuses, all good. Checked under the truck and all connection look good. Thinking is the trailer lamp lighting control module. Though of going to the dealer, but of course the truck just turned 38,000.
Has anyone else ran into this? I did search online and found 1 You-tube video where a guy cut one open all corroded.
I do live in Wisconsin and land of salt. When the truck was new I had the under side coated with rubberized rust proofing.

 

This is certainly not what we like to hear, Randy Platz.  Please know, customer satisfaction is extremely important to us. Our team would be more than happy to take a closer look into the concerns with your 2021 GMC AT4 2500 HD Duramax. To do so, please send an email to [email protected] with ATTN: Randy Platz/GM Trucks in the subject line.

Please include your contact information, VIN, a brief description of your concern, and the name of your preferred dealership. We look forward to hearing from you. To learn more about GM’s Privacy Policy, please visit https://www.gm.com/privacy-statement.html. The information you provide may be monitored and recorded and is subject to the GM Privacy Statement.
 
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[SWFL]

On 1/21/2023 at 1:56 PM, Randy Platz said:

Hello everyone.
I have a 2021 GMC 2500HD Duramax AT4. New Years eve treaded my truck to a touchless car wash. Drove home and parked in the garage (where it always parks) It sat until Monday. Upon start up in came up with a 3 messages, Check Trailer Right turn lamp, than Check Trailer Left turn lamp, then check Trail brake lamps. However there is no trailer connected. I thought maybe water in the 7 pin plug. Nope clear and dry, just a little dielectric. Check the trucks turn signals and they blink very fast light a burned out bulb. Checked all the fuses, all good. Checked under the truck and all connection look good. Thinking is the trailer lamp lighting control module. Though of going to the dealer, but of course the truck just turned 38,000.
Has anyone else ran into this? I did search online and found 1 You-tube video where a guy cut one open all corroded.
I do live in Wisconsin and land of salt. When the truck was new I had the under side coated with rubberized rust proofing.

 

Randy, did you find a fix for this? My 2020 Sierra just started giving me the exact same messages with fast blinking turn signals. Appreciate your response.