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What this part is and which trucks it fits

The Sequential LED Side View Turn Mirror Signal Light swaps the factory bulb in your mirror housing for an 18-LED sequential array. It is engineered for the GMT1XX platform: the 2020-2023 Chevrolet Silverado and the 2020-2023 GMC Sierra.

The compliance package covers SAE J1889 for LED photometry, SAE J578 for amber color at a 590-595 nm dominant wavelength, and FMVSS 108 Amendment 18. The Lexan™ 925AU polycarbonate lens carries a UV-stabilized AS-4000 hard-coat, validated to SAE J2527 accelerated weathering with a projected 10-year service life.

Quick answers before the detail

• Ready for CAN-bus 3.0? Yes. The PWM controller is CAN-FD tolerant per ISO 11898-1:2024, covering legacy GMLAN and the CAN-FD topologies Ford, GM, Toyota, and Tesla are adopting for 2026-2028.
• Hyperflash on a 2023 Silverado 1500 LTZ? No. The 6.2 Ω ± 0.3 Ω load emulates a 21W incandescent filament and is recognized by GM BCM P/N 13529828 and later revisions.
• UN R148 timing? 180 ms per segment fill rate, inside the 200 ms maximum in R148 Rev.4.
• Beam pattern legal? 95-110 cd at FMVSS 108 Category 1a, with ±20° horizontal and ±10° vertical spread.
• Splicing required? It is plug-and-play. Delphi/Aptiv GT 150-series sealed connectors plug straight into the stock harness.

Lens and housing: what the ratings rest on

Polycarbonate instead of acrylic

Most aftermarket mirror lenses are PMMA (acrylic). This one is injection-molded polycarbonate with a UV-cured AS-4000 hard-coat. The choice targets a documented failure mode on these trucks: acrylic lenses micro-craze under repetitive thermal cycling from -40°C to +105°C per GM GMW3172.

The housing is PBT-GF30, a 30% glass-fiber-reinforced composite with a heat deflection temperature of 210°C at 1.82 MPa (ISO 75/A). Lower-tier units warp at sustained under-hood-adjacent temperatures. This one holds shape well past that point.

Eighteen OSRAM LEDs, one Infineon driver

The array runs 18 OSRAM OSLON® Compact PL amber LEDs (peak λ = 592 nm) in six independently addressable segments, driven by an Infineon TLD5098EP boost-to-ground IC. Each segment fires at a 180 ms interval, producing the inward-to-outward sweep that R148 Rev.4 defines as dynamic signaling.

The driver IC adds load-dump protection to 40V survivability (ISO 16750-2:2023), reverse-polarity guarding, and open-load detection that stops the BCM from logging phantom bulb faults.

DTC codes this circuit prevents

GM body control modules check the turn signal circuits every drive cycle. The table maps the GMT1XX turn-signal codes to the mechanism inside this assembly that stops each code from setting.

Calibration note: on GM's 2024/2025 BCM calibration (TIS download P/N 13554018 or later), older resistor-pac signals set B3948 through B3951 on cold-start bulb checks. This assembly is validated against that calibration.

Spec comparison: Koeep vs GM OEM vs generic LED

The OE reference is GM P/N 84756983, a single-filament WY21W incandescent. Generic units typically run 6 to 12 unbranded 2835 SMD chips behind uncoated acrylic. The figures below come from the validation data.

Why cold mornings trip hyperflash on cheap modules

The symptom is specific: hyperflash that shows up only on cold mornings after generic sequential signals go in. This is documented 2023-2026 GMT1XX BCM behavior. Below 4°C ambient, the BCM runs a high-resolution resistance sweep at cold-start bulb check, sampling every 2 ms for 200 ms.

Simple parallel-resistor modules drift with temperature. Resistance drops 8-12% at 0°C versus 25°C, the reading slips under the BCM's 4.7 Ω minimum threshold, and the BCM calls it a dead bulb.

Fitment, OE cross-reference, and validation record

The SKU covers the 2020-2023 Chevrolet Silverado 1500/2500HD/3500HD and GMC Sierra 1500/2500HD/3500HD in every trim: WT, Custom, LT, RST, LTZ, High Country, SLE, SLT, AT4, and Denali. It replaces GM OE part numbers 84756983, 84756984, 84756985, and 84756986 across left/right and trim variants.

• Power folding (RPO DXL): compatible.
• Heated glass (RPO DLF): compatible.
• Blind-spot monitoring (RPO UKC): compatible, zero interference at the indicator LED.
• Surround-view camera (RPO UVS): compatible, puddle lamp circuits untouched.

DTC validation ran across GM BCM calibrations P/N 13529828 through 13554018 (2020-2026 model years) with zero fault codes in 500+ cold-start bulb-check cycles at -20°C, 23°C, and +65°C. The same low-side driver architecture appears in Ford (BCM P/N JL3Z-15604) and Toyota (BCM P/N 89200-0C) controllers, and the lens stack clears Ford WSS-M4D929-A and Toyota TSC7301G.

Longevity: 50,000 hours to L70 (IES TM-21-21) works out to 30+ years at average daily turn-signal use, and the electronics are rated for 15-year continuous operation per IEC 62380 / SN 29500. The line is maintained through 2030 with backward-compatible revisions as GM ships BCM updates.

More signal lighting from Koeep

Koeep covers bikes as well as trucks. Ducati riders can get the same integrated look with turn signal mirrors for the 959 Panigale (2015-2020) and 1299 (2015-2018) or LED turn signal rear view mirrors for the 899 Panigale and 1199 (2012-15). Both sit in the body parts collection alongside the rest of our auto and motorcycle body components.

Working an older GM truck instead? The complete guide to the driver side power heated tow mirror for 2000-2002 Chevy GMC (Black Smooth) walks through that swap.

Frequently asked questions