2011 Chevrolet Silverado 1500 P0572 Code: Trailer Brake System Fault and Electric Brakes Not Engaging

I'm confused—instead of clearing the code, why not address the root cause? Have you added any LED bulbs to the brake light assembly? DTC P0572 indicates a low voltage on the brake switch circuit. The ECM detects a signal below threshold for more than 2 seconds when the BCM confirms brakes are applied. This DTC is set if the condition occurs in at least 8 out of 10 instances.

I understand—my goal is to fix the actual issue, not just clear the warning. I haven't installed any LED bulbs. I've read elsewhere that a faulty brake switch could be the cause; however, if it were defective, I'd expect more noticeable symptoms like non-responsive brakes or inconsistent lighting. What are your thoughts on this possibility?

This resource may help: https://www.obd-codes.com/p0572

Check the brake switch voltage at specific terminals. The brake switch signal wire is typically light blue/white, connected to ECM X1 connector pin 9 and trailer brake module pin 37. When brakes are applied, this wire should read battery voltage (around 12V). Use a multimeter with battery negative as ground for accurate readings. Also, consider that other modules may store related fault codes.

Thanks, Autojoe! That's very helpful. I'll need to invest in a better OBD2 scanner to check for additional stored codes. After work this week, I plan to test the voltage at those specified terminals.

I use the Autel MD805 scanner—it supports reading codes from multiple vehicle modules and has received positive reviews. You can search online for user reviews or watch YouTube videos for real-world performance. I previously owned a more expensive Snap-on device, but the Autel is reliable and affordable.

Last night, my local mechanic scanned the system and found another code: C0900. He said it might be insignificant. Unfortunately, right after he finished, my battery died—this was the original battery—and I suspect it was weakening. I replaced it last night. Does DTC P0572 require a certain amount of driving to clear, or must it be manually cleared? Could a weak battery cause electrical instability affecting the brake system?

Verify both battery voltage and charging system output. As your mechanic noted, C0900 may not be critical. Have you tested the brake switch signal voltage at the correct terminals when brakes are applied?

I haven't yet measured the brake switch voltage. It will be part of my weekend project—I'll update this thread with results once I complete the test.

chstni wrote: Mon Mar 18, 2019 3:43 pm My 2011 Chevrolet Silverado 1500 has a factory-installed trailer brake controller. I've been getting a "Service Trailer Brake System" warning on the dashboard. To clear it, I just press any scroll button and it goes away. I have replaced (twice) a module under the spare tire (part # GM 20904439). It helped—reduced frequency—after the last replacement, the code only appears immediately after startup but clears and does not return until I restart the vehicle. The truck's brakes work normally, lights function correctly, cruise control works fine. The issue is that my RV trailer's electric brakes do not engage when I press the truck's brake pedal. I recently adjusted the trailer brakes assuming wear was the cause, but after proper adjustment, connecting the trailer and applying brakes resulted in no response. With the trailer disconnected, I measured the 7-pin connector (electric brake and common) using a multimeter—read only 1.7V DC, which does not change when braking is applied. I'm trying to avoid dealer repair fees and would greatly appreciate any input. Thanks, Steve Thanks for the responses! I have the same issue.