Service trailer brakes soon, warning comes across display & loss of trailer brakes without warning. i was driving on a bright sunny day, dry roads, traffic ahead of me came to a stop. i was pulling a 7,000 pound travel trailer stepped on brake all was fine 1 minute, service trailer brake soon warning display came across & no trailer brakes & almost caused an accident. as long as the display says service trailer brakes soon, you have no trailer brakes, there is no warning or back up system just hope for the best, just glad i wasn't going down a mountain. this time i went to have oil changed & service trailer brakes soon displayed & truck ran rough. took it to the dealership, after 3 days at dealership, mechanic says the "fuel pump flow control module" has to be replaced, same as in recall # 14515b. this warning will also display without trailer connection & vehicle power loss happens until restarted. this is dangerous as there's no warning or certain situation or weather condition that makes this any different. this happens whether your city or highway driving, doesn't matter.
The brake master cylinder on the vehicle leaks brake fluid past the rear seal into the vacuum power brake booster. the fluid will cause the diaphragm in the booster to fail. the only way to check for a leak is to remove the vacuum hose and see if it is wet or to continue to add brake fluid until the booster is full of fluid at which a leak will become visible.
Failure of cruise control and trailer braking system while braking. issue was a break in the wiring harness under the dash causing a short. broken wire still had insulator in tact as if new. this seems to be an issue due to type or undersized wire as this is the second harness failure on the truck
While in motion at multiple speeds, brakes would surge or feel solid with minimal braking intermittently. when replacing the brake booster we noticed the master cylinder was leaking into the brake booster causing the issues. this could be very dangerous. did not matter if turning or straight. worst part is it seemed to fail upon heavier application of brakes when needed most. this has been happening since about 15,000 miles