B2575 on 2015-2019 GMC Sierra 2500: Headlamp Control Circuit Fault Explained

What's Unique About the 2015-2019 Gmc SIERRA 2500

For this generation of GMC Sierra HD trucks (and their Chevrolet Silverado platform mates), code B2575 is overwhelmingly associated with aftermarket snowplow installations. The truck's BCM is highly sensitive and can interpret the electrical signals from a snowplow's headlight changeover module as a short circuit, triggering the code. This is so common that General Motors has issued multiple Technical Service Bulletins (TSBs), such as PIT5412D, stating the issue is often with the upfitter's equipment, not a fault in the truck's factory components. Unlike older vehicles, these trucks do not use simple relays for the headlights; control is integrated directly into the BCM, which acts as a solid-state driver.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Left low-beam headlight is inoperative or works intermittently.
• Headlights flicker, especially when switching between the truck's factory lights and snowplow lights.
• A "Headlight inoperative" message may appear on the Driver Information Center (DIC).
• In some cases, the headlight may stay on and cannot be turned off.
• With a plow installed, headlights may shut off completely when switching from high beams to low beams.

Most Likely Causes

1. Improperly Installed or Faulty Snowplow/Aftermarket Lighting 🔴 High Probability As documented in GM TSBs PIT5412D and GM Upfitter Bulletin #116, the BCM is sensitive to the electrical load and timing of aftermarket headlight switching modules. The BCM's diagnostic algorithm can misinterpret the delayed current draw from these modules as a short circuit. Plow manufacturers like BOSS, Fisher, and Western have released specific procedures and updated harnesses to address this.
   How to confirm: If a snowplow is installed, disconnect its lighting module entirely from the truck's wiring. Clear the codes and see if the factory headlights function normally. A hard reset (disconnecting the battery) may be needed to reset the BCM's protected driver circuit. If the lights work, the fault is in the plow's system.
   Typical fix: Contact the snowplow manufacturer (e.g., Fisher, Western, BOSS, SnowEx) for an updated wiring harness or isolation module specifically designed for 2015+ GM trucks. 🎬 Watch: How to fix common electrical issues with snowplow lighting. For example, Western/Fisher offers kit #69818-2 for trucks with HIR2 bulbs, which includes sealed relays to prevent this issue. Ensure installation follows GM Upfitter Bulletin #116, which advises against any switching delay after the BCM commands the lights on.
   Est. part cost: $100-$400
2. Burnt-out Headlight Bulb or Incompatible Aftermarket Bulb 🟡 Medium Probability → Shop Headlight Bulb A standard halogen bulb can burn out, creating an open circuit. Some aftermarket LED or HID bulbs can have incorrect resistance values or cause current draw patterns that the BCM may interpret as a fault.
   How to confirm: Visually inspect the bulb. Swap the left low-beam bulb with the known-good bulb from the right side. If the problem moves to the right side (now showing code B2699), the bulb is bad. 🎬 Watch: Troubleshooting guide for Sierra headlights that won't turn on.
   Typical fix: Replace the headlight bulb with a new, high-quality OEM or equivalent bulb. The 2015-2019 Sierra 2500 typically uses a 9012 (HIR2) bulb for both low and high beams in a single projector, but this can vary by trim.
   Est. part cost: $20-$50
3. Damaged Headlight Connector or Wiring 🟡 Medium Probability The connector at the back of the headlight assembly is exposed to heat and moisture, which can lead to corrosion, melting, or loose pins over time. This is a known failure point on these trucks, even without a plow.
   How to confirm: Unplug the connector from the headlight assembly and inspect it for any signs of melting, charring, green or white corrosion, or backed-out pins. A melted connector is a very common find.
   Typical fix: If the connector is damaged, replace it with a new pigtail connector, which involves cutting the old one off and splicing the new one in. Use heat shrink connectors for a durable, weather-resistant repair. Common replacement part numbers include ACDelco PT2448 and Dorman equivalents. 🎬 See this walkthrough on diagnosing common Silverado and Sierra headlight failures.
   Est. part cost: $15-$45
4. Blown Fuse ⚪ Low Probability An electrical short in the circuit will cause the protective fuse to blow. This often points to a larger issue like melted wiring.
   How to confirm: Locate the underhood fuse block. For 2015-2016 models, check the double fuse F59. For 2017-2019 models, check F58. These are often pink or light brown Miku-style fuses. Test for continuity.
   Typical fix: Replace the blown fuse. If it blows again immediately, there is an active short circuit that must be found and repaired. Do not simply install a larger fuse.
   Est. part cost: $1-$5

Rare But Worth Checking

• Faulty Body Control Module (BCM): → Shop Body Control Module This is rare and should only be considered after all other possibilities (especially upfitter wiring, the bulb, and the connector) have been exhaustively ruled out. The BCM is expensive and requires dealer programming. Misdiagnosing a plow wiring issue as a bad BCM is a very common and costly mistake.

Diagnosis Steps

1. Scan the Body Control Module (BCM) for codes. Confirm if B2575 is active and if B2699 (right side) is also present.
2. If a snowplow or other front-end electrical accessory is installed, this is your primary suspect. Completely disconnect the accessory's lighting harness from the vehicle's factory wiring.
3. After disconnecting accessories, clear the codes. A hard reset may be necessary: disconnect the negative battery terminal for at least 30 seconds to reset the BCM's protected circuits. Then, check if the factory headlights now work correctly. If they do, the fault lies with the accessory's wiring or module.
4. If no accessories are installed, begin with the simplest components. Inspect the left low-beam headlight bulb. Swap it with the right side's bulb to see if the fault follows the bulb.
5. Carefully inspect the headlight electrical connector for any signs of melting, corrosion, or damaged pins. This is a common failure point.
6. Check the fuses for the left headlight in the under-hood fuse block (F59 for '15-'16, F58 for '17-'19).
7. Using a multimeter, check for proper voltage and ground at the headlight connector according to the vehicle's wiring diagram. Check ground point G106 (located at the front of the engine compartment) for corrosion or looseness.
8. If all wiring, connectors, and the bulb are confirmed to be good, the Body Control Module (BCM) may be faulty, which requires professional diagnosis with advanced scan tools.

Parts You'll Likely Need

• Snowplow Lighting Harness/Module (OEM #Varies by plow manufacturer (e.g., Western/Fisher #69818-2)) — This is the most common cause of code B2575 on these trucks, as documented by GM TSBs. The fix is often an updated part from the snowplow manufacturer (e.g., Fisher, Western, Boss, SnowEx) that includes an isolation module or sealed relays.
  Trusted brands: Western, Fisher, BOSS, SnowEx
  Aftermarket price range: $150-$400
• Headlight Bulb (OEM #ACDelco 9012 (HIR2)) — A burnt-out bulb creates an open circuit, which is a common and simple cause for this code if no plow is installed. The typical bulb is a 9012 (HIR2).
  Trusted brands: ACDelco, Sylvania, Philips
  OEM price range: $30-$50
  Aftermarket price range: $20-$40
• Headlight Connector Pigtail (OEM #ACDelco PT2448) — The connector can melt or corrode, causing a poor connection and triggering the fault code. This is a common failure point.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$45
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• B2699 — B2699 is the identical fault but for the Right Headlamp Control Circuit. Seeing B2575 and B2699 together strongly points to a systemic issue, almost certainly related to an aftermarket snowplow installation affecting both headlight circuits.

Technical Service Bulletins (TSBs) & Recalls

• PIT5412D: Addresses flickering or inoperative truck or snowplow headlights, explicitly stating it is not a truck issue but an upfitter issue.
• PIT5412A: Earlier version of the TSB pointing technicians to GM Upfitter Bulletin #116.
• GM Upfitter Bulletin #116: Provides the technical explanation for why the BCM sets codes B2575/B2699 with plow lights. It details the BCM's current-sensing diagnostic strategy and the need for instantaneous headlight switching to avoid triggering a fault.

Platform-Specific Known Issues

• Snowplow Prep Package Sensitivity: The Body Control Module on these trucks is known to be sensitive to the electrical characteristics of aftermarket lighting systems, particularly snowplow headlight switching modules. This is documented in TSBs #PIT5412D and #PIT5412A.
• GM Upfitter Bulletin #116: This critical document explains the BCM's headlight diagnostic logic. It states that any switching from truck to plow lights must happen instantly when the BCM commands the lights on. Any delay will be seen as a short circuit, setting a DTC and disabling the circuit. The ignition and headlights should be OFF when connecting or disconnecting the plow harness.

Mechanic-Grade Diagnostic Values

• BCM Operating Voltage — expected: 9.0 - 16.0 Volts. Failure: Operating outside this range can cause erratic BCM behavior, including setting false fault codes.

Hidden / Shadow Codes Worth Checking

• B2575 01: Left Headlamp Control Circuit Short to Voltage. This indicates the BCM has detected battery voltage on the control circuit when it should not be present. (see via A professional-grade scan tool like the GM GDS2 (Global Diagnostic System 2) is required to read these two-digit symptom codes.)
• B2575 02: Left Headlamp Control Circuit Short to Ground. This indicates the control wire is shorted to the vehicle's chassis or another ground path. (see via A professional-grade scan tool like the GM GDS2 is required to read these two-digit symptom codes.)

Scan Tool Commands That Help

• GM GDS2 (or equivalent professional scan tool): BCM Output Control > Exterior Lighting > Left Low Beam Headlamp — This bidirectional command allows a technician to manually command the left low beam headlamp ON and OFF directly from the scan tool. If the headlight activates with the scan tool but not the switch, it helps isolate the problem to the switch or its input circuit. If it fails to activate, it confirms a fault in the BCM's output driver, the wiring, or the headlamp itself.
• GM GDS2 (or equivalent professional scan tool): Clear Codes / Reset BCM — After a repair, the BCM's protected driver for the headlight circuit may remain disabled even if the fault is fixed. A scan tool can clear the DTC and reset the module. If a scan tool is unavailable, disconnecting the battery for at least 30 seconds can perform a hard reset of the module.

Wiring & Ground Locations

• G106 — Located at the front of the engine compartment, on the frame rail. This is the primary ground for the left headlamp assembly.. A loose or corroded G106 ground will cause high resistance or an open circuit for the left headlamp, directly causing intermittent operation or failure and triggering code B2575.
• G103 — Located on the front of the passenger-side (right) cylinder head.. This is a major engine and chassis ground point. While a fault here would likely cause numerous other issues beyond just a single headlight, poor grounding can contribute to erratic electrical behavior and should be checked for tightness and corrosion.
• K9 BCM Connector X5 — One of the large multi-pin connectors on the Body Control Module (BCM), which is typically located under the driver's side of the dashboard.. The control wire for the left low-beam headlamp originates from a pin on this connector. When performing advanced diagnostics, a technician would test for voltage and continuity at this specific pin to determine if the BCM is sending the correct signal.

Real Owner Repair Stories

• Reddit user post (Not specified, but within the 2015-2019 generation) — Headlight went out.
  ❌ Tried (didn't work) Initially assumed it was just a burnt-out bulb.
  ✅ What actually fixed it Upon inspection, the headlight connector was found to be melted. The user purchased a replacement headlight connector pigtail from a local auto parts store, cut off the old melted connector, and spliced the new one in.

OEM Part Supersession History

• PT1449 → PT2448 — General part number update and consolidation by ACDelco.
  Heads up: ACDelco PT2448 is the current GM Original Equipment service part for the 4-pin headlight connector pigtail. It may also be cross-referenced with interchange numbers like 15306396 and 19180287.

Model Year Variations Within This Range

• 2015-2016 vs 2017-2019: The underhood fuse block layout was revised. The fuse for the left low-beam headlamp is F59 on 2015-2016 models and F58 on 2017-2019 models.
• 2015-2019 (by trim): Headlight technology varies significantly by trim level (Halogen, HID, LED). They are not interchangeable without custom wiring and BCM reprogramming. Code B2575 is most commonly associated with the base halogen systems, particularly when aftermarket equipment like snowplows are added.