Silverado Tow Vehicle: Service Trailer Brake System?

We had a similar problem. Cleaned out the 7 pin and the problem went away.

Was going to say....most of these problems are at the connector

I had a problem last year that may or may not relate to the OP's

From a post I made at the time:


"..... trouble shooting story. Went over everything several times and decided the trailer brakes must be ok since the breakaway system engaged full braking ( Trimetric showed 12 amps for brakes and it would not move when towed a little with the 7-pin disconnected)

Checked both ends of the trailer 7-pin and after some confusion (more on that) it was ok, so now we are into the truck. Much back and forth trying things with the controller wiring and truck 7-pin, very frustrating, turned out to be intermittent low 12v power to the controller.

By this time I had bought a replacement controller. Hopkins "Impulse" time based, has a digital readout. So wiring that I had to check the adapter wire set that goes from the controller's four wire plug to the truck's socket (different adapters needed for Chev, Ford, etc) so I had the Chev one already for the Voyager. I cut and spliced the four wires at the controller end to the adapter and plugged in, no joy. Got the controller fault code SC which means the brake wire is bad, or bad magnet or 7-pin connector bad on blue wire. Checked all that again, no joy. Also it chattered and buzzed badly when manual pushed.

Undid the four wire splice on ground and 12v pos wires and jumpered to battery direct with standard jumper cable set. Bingo! It all worked properly. Tried it with only the ground jumpered, no joy. So the 12v pos was guilty!

More snooping at the truck's end where the controller adapter plug goes into a "Trailer 6 Pin" socket. Turned out there was only 2 volts on the positive pin in the 6-pin socket (of which only four pins are used) plus that was intermittent.

Could not figure out from the truck's diagrams in the manual which fuse works that 6-pin's positive and all fuses checked ok. Very frustrating all round.

Fix chosen was to take out the whole thing on the floor (by left foot) which has that Trailer 6-pin socket and on the back of the whole thing is a fat red wire I tapped into and jumpered to the black controller wire, and still used the 6-pin plug for the other three wires. Ta da! The Hopkins now acts right"

Since then I have been using the Hopkins controller instead of putting the Voyager back in. No electrical problems, but the Voyager was a bit smoother I think.

What timing, I had the same problem and did some research on it and thought it might be the brake switch. I had some other issues with my Silverado so I took it to the shop this week and sure enought that is what it was.

evanrem wrote:
What timing, I had the same problem and did some research on it and thought it might be the brake switch. I had some other issues with my Silverado so I took it to the shop this week and sure enought that is what it was.

Is the brake switch accessible from in the cab? I think on my truck there is no brake switch - the code C0131 says "master cylinder pressure sensor intermittent". On my previous TV there was a switch and the aftermarket controller used inertial sensor to adjust trailer brake output but my current TV knows how hard I'm pressing on the pedal.

For other responders, the error occurs without the trailer hooked up so it's not the 7-pin connector.

I took it to the dealer to repair. As it suspected, it was the master cylinder pressure sensor.