Aaustins14

2014 Sierra 4.3l V6 First time loaded up with a trailer since last fall and I'm experiencing a flashing check engine (p0300) with no hard codes set. Will flash for 5-30 seconds and turn off. When its flashing it is definitely low on power and feels sluggish. Brand new plugs and wires (within a month or so) New-ish fuel pressure sensor on the fuel line. (Not GM part, cheapo from autozone) New fuel pump (1.5 years old)(GM Part) It happens under acceleration. It happened once on the on ramp to the highway, and happened twice pulling away from a stop under decent acceleration. It also happened once on the highway, torque converter locked, rolling into the throttle. I did a test with no trailer hooked up, just driving around. Plugged cheapo scan tool in and monitored the fuel pressure. Cruising on the highway at 60mph my fuel pressure bounces between 37-53psi. On steady acceleration is see it sometimes dropping as low as 33 psi and hanging out there for a while (maybe 8-10 seconds). That is on steady acceleration, not just spike the RPMs and the pressure drops as the pump catches up. Any ideas other than fuel? Do those fuel pressure numbers seem low or am I stretching it? As always, Any ideas help! Thanks

Follow Up: Ended up pulling the trigger and replacing the Trailer brake control module under the bed by the spare tire. Solved my issue. Thanks for all your input.

I know this is an old thread. Sorry. Im looking for the part number for the fuel pressure sensor in question in this post. The one on the fuel rail by the frame. Drivers side, roughly under the drivers seat. I cannot find a diagram that shows that sensor on the fuel line.

I will try that distilled water trick. I haven't tried much to get it removed because I didn't want to make it worse. Once summer comes and I start towing again, I might just have to start throwing parts at it.

My third brake light leaked on the previous owner, I have some water stains to prove it. It seems he must have fixed it because it has not leaked in the time I have owned the truck. Winter here in Western NY. I think you may be on to something with the cold weather. I did notice it started happening repetitively once the temperatures dropped. I still need to order the control module, but I would also like to order that connector and do both of them. Just cannot seem to find the connector online or even a part number. I do think that my issue is from the control module. Either water got in, or it just failed on its own.

Well I currently have the In-cab trailer brake controller unplugged. This stops the constant beeping, now it only beeps once when the truck is started. My battery seems fine. Voltage was fine. and the truck has been starting just fine in the -5f degree weather. I am believing that it is the trailer brake control module that is under the truck/above the spare tire. I have not gotten around to changing it out, mainly because it is a frozen tundra out there. I already changed out the in-cab controller and the connector on the back bumper. If is is not the control module, then I probably have a bad wire hardness somewhere.

I will go through those.. Thank you. Nice website to keep bookmarked. One thing I do notice is that a lot of the TSB's are talking about this issue when a trailer is connected. I have no trailer connected. I did think about electrical/voltage issues. I can check the age of the battery after work tonight. I have not had any long cranks or old battery indicators, but worth a check.

Update... So I got the new manual brake controller and installed it. Nothing changed, seems to be reacting the same. Randomly throwing "Service trailer brake system" and "Check trailer wiring." It doesn't seem to be linked to movement like a chaffed wire. It happed a handful of times before I even put it in drive. It also happened sitting at a stop light after I had been sitting there for a while. Checked again for bad/chaffed wires. Should I just bite the bullet and order the trailer brake controller?? I really hate the brake out the parts cannon. Any suggestions are much appreciated

OK, So I unplugged the manual trailer brake controller in the cab. Now the only warning is the warning immediately after I start the truck. This warning was there before I unplugged it. Drove around today with no issues except the warning on startup. I am hoping that the controller is the issue. My other thought is that with it unplugged the entire trailer brake system is disabled and thats why the warnings stopped?? I am going to order a new one and see what codes remain after installing it.

@M1ck3y I have checked over a lot of the visible wiring harness and found nothing. A lot of the harness is covered in wire loom so it is hard to tell, but I didn't see any chaffing. My understanding with that last code was that the Chassis couldn't talk to the Trailer brake module..? I guess it could be either of them or wires in between. Someone would have to really understand the system and how their networked to figure that out. That article only references the 2013/14 Silverado/Sierra HD trucks.. So wouldn't be applicable. Thanks for the ideas @OffTheAir Yea. Its driving me nuts. I did check all the fuses that seemed to be related to anything trailer or braking and they were all ok. I will look into the on dash controller.. Maybe ill try unplugging it and see if it improves. Thanks for all the ideas. They are appreciated.

Thanks Mickey

Ok everyone, new here. I tried my hardest to avoid posting because I know that there are a thousand threads on the internet regarding the chime for "Service Trailer Brake System" and "Check trailer wiring". I have intermittently had the Service trailer brake system and check trailer wiring warning come on the screen for maybe a year. It would pop up maybe once or twice a month. The problem is that this week it must have went off hundreds of times. It has never gone off while pulling a trailer, it only ever happens driving empty. Today on my drive home from work it chimed at me from key on to key off when I got home. It was very rainy so could be a wiring issue. It beeps back and forth between the two warnings the entire drive. The truck does have a brand new 7pin/4pin trailer connector I installed in the rear bumper, so I know it isn't that. I also unplugged the Trailer Brake Module above the spare tire and cleaned and added dielectric grease. I looked for corroded wires but did not see any. Is there a particular place to look? Any help is appreciated, I'm at my wits end. Thanks in advance EDIT : Forgot I scanned the chassis control module.. Came up with these codes: c1114-00 c1115-5a c1116-00 c1117-00 u1556-0 EDIT: 2014 GMC Sierra 1500