B2605 on 2015-2017 Chevrolet Tahoe: Right DRL Circuit Fault Causes and Fixes

What's Unique About the 2015-2017 Chevrolet TAHOE

The K2XX platform, which includes the 2015-2017 Tahoe, is known for a specific manufacturing flaw that is the root cause of this code and many other electrical issues. A crucial Body Control Module ground point (G218) located under the driver's side dash was often assembled with sound-deadening insulation material trapped between the ground connector and the vehicle body. This creates high resistance, leading to a cascade of seemingly random electrical faults, with the B2605 DRL code being a common symptom. This issue is so prevalent that it is documented in multiple Technical Service Bulletins.

Diagnostic Flowchart

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

Symptoms You May Notice

• Right Daytime Running Lamp (DRL) is not working
• Service Stabilitrak message on the dash
• Instrument panel cluster goes blank or flickers
• Radio or center display screen goes blank
• Loss of electric power steering assist, or jerking/kicking in the steering wheel
• Engine may stall intermittently
• Multiple other warning lights and seemingly unrelated trouble codes appearing at the same time
• Wipers continuing to run after being turned off
• Alarm sounding randomly when locking doors

Most Likely Causes

1. Poor Body Control Module (BCM) Ground at G218 🔴 High Probability A known issue documented in GM Technical Service Bulletins (PIT5405 series) where dash insulation material gets trapped under the ground eyelet during assembly, causing a poor connection. This is the most common cause for a wide array of electrical issues on this platform.
   How to confirm: Visually inspect the G218 ground stud located under the driver's side dash. It is high up on the A-pillar, to the left of the brake pedal, often hidden behind the dash speaker grille area. Check if the black, fibrous dash insulator mat is pinched under the ground's ring terminal. The 10mm nut may also be loose.
   Typical fix: Disconnect the battery. Remove the 10mm nut, pull the ring terminal(s) off the stud, and use a utility knife to cut away the section of insulation mat that is interfering. Scuff the ring terminal and the body surface with sandpaper or a wire brush to ensure clean metal-to-metal contact, then securely reinstall and tighten the nut.
   Est. part cost: $0-$5
2. Damaged or Corroded Headlight/Fascia Wiring 🟡 Medium Probability The front fascia wiring harness and its connectors are exposed to the elements. Water intrusion can cause corrosion in the headlight connector pins, and road debris or improper repairs can lead to chafed or broken wires. A similar issue with the harness chafing on the bumper bar is noted in TSB PIT5487F for the left DRL (B2600), indicating a vulnerability in this area.
   How to confirm: Unplug the main connector (X120) at the back of the right headlight assembly. Inspect for any green or white corrosion on the pins, pushed-out pins, or visible damage to the wires leading to the connector. Trace the harness as best as possible to look for signs of rubbing or chafing against the frame or bumper supports.
   Typical fix: Clean corroded terminals using an electrical contact cleaner and a small brush. If the connector or wiring is severely damaged, it may require replacement or splicing in a new pigtail connector, such as an ACDelco PT2448 or equivalent.
   Est. part cost: $15-$50
3. Failed DRL LED Driver/Module or Bulb ⚪ Low Probability While the LEDs are long-lasting, the small circuit board (driver) that powers them can fail due to moisture intrusion or vibration, causing corrosion on the board itself. This is less common than the ground or wiring issues.
   How to confirm: If the G218 ground and wiring are confirmed good, the fault is likely internal to the headlight assembly. This is difficult to confirm without swapping with a known-good headlight assembly from the other side of the vehicle or a new part.
   Typical fix: Official repair is to replace the entire headlight assembly. Some DIY-ers have successfully opened the headlight housing to repair or replace the small internal LED driver board, but this is a complex and delicate procedure. 🎬 See how to repair the internal DRL LED driver board.
   Est. part cost: $300-$900

Rare But Worth Checking

• Faulty Body Control Module (BCM): This is very rare. The BCM is a robust component. Before condemning the BCM, all other possibilities, especially the G218 ground and all related wiring, must be exhaustively checked. The presence of multiple unrelated codes points away from a single faulty module and towards a systemic power/ground issue.

Diagnosis Steps

1. Scan the vehicle for all DTCs in all modules. Note if multiple B-codes, U-codes, and C-codes are present, as this strongly points to a systemic electrical issue like the G218 ground fault.
2. RECOMMENDED: Disconnect the negative battery terminal before proceeding.
3. Locate the G218 ground stud. It is on the driver's side, high up under the dash near the A-pillar, sometimes accessible by removing the side dash panel or the speaker grille.
4. Remove the plastic trim panels to gain access. This may involve pulling off the A-pillar handle cover, removing two 10mm bolts, and carefully unclipping the dash-end trim piece.
5. Inspect the ground connection. Check if the black dash insulation mat is pinched between the metal ring terminal and the vehicle body.
6. Disconnect the 10mm nut and remove the ground terminal(s).
7. Carefully cut away the insulation mat around the stud with a utility knife to ensure it cannot interfere with the connection.
8. Clean the ring terminal(s) and the body surface with a wire brush or sandpaper to ensure a bright, clean metal-to-metal contact.
9. Securely reinstall the ground terminal(s) and tighten the nut. Ensure it is snug and does not rotate.
10. Reconnect the battery, clear all DTCs, and start the vehicle. Check if the right DRL now functions and if other electrical symptoms have disappeared.
11. If the problem persists, unplug the right headlight connector (X120) and inspect the wiring and connector pins for corrosion, damage, or pushed-out pins.
12. If wiring is good, consider testing the DRL circuit for power and ground at the connector before condemning the headlight assembly.
🎬 Watch: Step-by-step guide to testing your OEM Xenon headlight.

Parts You'll Likely Need

• No parts needed — The most common fix is repairing the existing G218 ground connection, which does not require any new parts.
  OEM price range: $0
  Aftermarket price range: $0
• Headlight Assembly (Right) (OEM #23388268) — Required if the internal DRL LED driver has failed and the ground/wiring are confirmed to be good.
  Trusted brands: ACDelco, TYC
  OEM price range: $500-$800
  Aftermarket price range: $250-$450
• Headlight Connector Pigtail (OEM #ACDelco PT2448 (verify pin count)) — Needed if the headlight electrical connector is melted, corroded, or the wires are broken at the connector body.
  Trusted brands: ACDelco, Dorman
  OEM price range: $40-$60
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus A Off
• U0140 — Lost Communication With Body Control Module
• C0544 — Steering Wheel Angle Sensor Circuit
• C0710 — Steering Position Signal
• B127B — Steering Wheel Controls Circuit
• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module
• U0100 — Lost Communication With ECM/PCM

Technical Service Bulletins (TSBs) & Recalls

• PIT5405C: Lists numerous DTCs, including B2605, caused by a poor BCM ground at G218 due to trapped dash insulation.

Platform-Specific Known Issues

• Technical Service Bulletin PIT5405C directly addresses the cluster of electrical issues, including code B2605, stemming from the poor G218 ground connection.
• Owner Experience: A user on Reddit with a 2016 Tahoe described a year-long battle with a dealer over random 'Service Stabilitrak' messages, power steering loss, and the radio staying on, all classic symptoms of the G218 fault.
• Owner Experience: On the TahoeYukonForum, a user reported that after experiencing flickering lights and random warning messages, they located and tightened loose ground bolts under the dash which completely resolved the problem.

Mechanic-Grade Diagnostic Values

• DRL Circuit Voltage (at headlight connector) — expected: Approximately 9V when DRLs are commanded on (for non-LTZ models where low-beam acts as DRL), or 12V for LED strip DRLs. Should be 0V when off.. Failure: 0V when commanded on indicates an open circuit or bad ground. Constant voltage indicates a short to power.
• Ground Circuit Resistance (at G218) — expected: Less than 1.0 Ohm between the ground eyelet and a clean chassis point.. Failure: High or infinite resistance indicates a poor ground connection, which is the primary cause of B2605.

Scan Tool Commands That Help

• GDS2 (Global Diagnostic System 2): Module Diagnostics > Body Control Module > Control Functions > Right DRL Command — After checking the G218 ground, use this command to manually turn the right DRL on and off. If the lamp responds to the scan tool but not the vehicle's automatic controls, it confirms the BCM, wiring, and DRL assembly are functional, pointing the diagnosis toward an input or configuration issue.

Wiring & Ground Locations

• G218 — Under the driver's side dash, high on the A-pillar to the left of the brake pedal.. This is the primary ground for the Body Control Module (BCM). When compromised by trapped dash insulation, it causes B2605 and a host of other electrical faults described in TSB PIT5405C.
• X120 — The main electrical connector at the back of the right (passenger side) headlight assembly.. This is the final connection point to the DRL. Testing for power and ground here can isolate the fault to the headlight assembly itself or the wiring leading to it.
• BCM Connector X5, Pin 1 — On the Body Control Module, which is located behind the lower left side of the dash.. This specific pin is the BCM's control output for the Right Daytime Running Lamp. The wire is typically White/Violet. Testing for voltage here can confirm if the BCM is attempting to send the signal.
• Headlight Connector X120, Pin 6 — At the right headlight connector.. On models with the LED strip DRL (like LTZ/Premier), this pin (typically a Gray wire) carries the signal for the LED strip.
• Headlight Connector X120, Pin 2 — At the right headlight connector.. On models where the low beam bulb serves as the DRL (like LS/LT), this pin (typically a Yellow wire) carries the DRL signal.

Real Owner Repair Stories

• Reddit user in r/ChevyTahoe (2016 Chevrolet Tahoe) — Service Stabilitrak message, steering wheel jerking/locking up, headlights pulsing, engine dying and restarting, all gauges resetting.
  ❌ Tried (didn't work) Replacing the main battery ground cable (worked temporarily), Dealer suggested replacing the alternator for 'overcharging'
  ✅ What actually fixed it The user found information about the G218 ground under the dash. After removing dash pieces, cutting back the insulation that was interfering with the ground connection, and re-securing it, the problems were resolved. This aligns perfectly with TSB PIT5405C.
• Reddit user in r/ChevyTahoe (2016 Chevrolet Tahoe LTZ, 146k miles) — Sudden cascade of errors: 'service side detection, stability track, service back camera, service airbag, tire pressure, lift gate, park assist'. All gauges dropped to 0 while driving. Radio screen went black. Intermittent no-start condition.
  ❌ Tried (didn't work) Dealer suggested a new battery but was not convinced., Dealer wanted $300 to diagnose the intermittent issue.
  ✅ What actually fixed it Another user in the thread suggested checking the main battery negative cable for a weak factory crimp. The user also mentioned the G218 ground as a known cause for these exact symptoms, pointing toward a systemic ground issue rather than a faulty component.

Model Year Variations Within This Range

• 2015-2017: The top trim level was named 'LTZ' for 2015-2016 and renamed 'Premier' for 2017. This is primarily a name change, but packages could differ slightly. The core electrical system related to code B2605 remained consistent.
• 2015-2017: On LS and LT trims, the low beam headlight bulb often serves as the DRL, running at a lower voltage. On LTZ and Premier trims, the dedicated LED accent strip serves as the DRL. This affects which pin at the headlight connector (X120) is active for the DRL function.