Rear Wiring Harness for Tesla Model S (2016-2021) - Front Radar Bumper | 1004421-04-T

The Unsung Link Between Rear Systems and Radar Precision

What It Actually Does (In Simple Terms)

• Rear Light-Radar Sync: When the front radar triggers an emergency brake, this harness tells your rear hazard lights to flash immediately—warning drivers behind you in the same split second. A faulty harness? It could delay that warning by a full second, enough for a rear-end crash.
• Backup Safety Coordination: When reversing, it connects rear parking sensors to the front radar system, so your Model S “sees” both what’s behind you and cross-traffic approaching from the front. No more blind spots during tricky parking maneuvers.
• Steady Power to Rear Sensors: Delivers consistent voltage to rear collision sensors and the backup camera, ensuring they don’t flicker or fail in extreme weather—whether you’re in a heatwave or a blizzard.
• Trunk Release Integration: Links the trunk’s electronic release to the bumper’s sensor array, so if you’re loading cargo, the harness prevents accidental trunk opening when the radar detects nearby obstacles.

How to Tell It’s Time to Replace

• Rear Lights Lag During Emergencies: Hazard lights take a beat to flash when you brake hard. That delay could mean the harness is slow to transmit the radar’s “emergency” signal.
• Backup Confusion: The screen shows rear sensor alerts but misses cross-traffic that the front radar should catch. The harness likely isn’t bridging the two systems.
• Trunk Glitches: The trunk won’t open with the button, or opens when it shouldn’t (like when you’re standing too close). The harness connects the trunk release to obstacle sensors—if it’s faulty, expect misfires.
• Random “Rear System Unavailable” Alerts: These pop up in dry weather, even after cleaning sensors. The harness is probably frayed, causing intermittent signal loss.

Why It’s Built Better Than Aftermarket Options

• Dual-Shielded Wires: Each wire is wrapped in foil and braided metal to block interference from your Model S’s high-voltage battery and motors. No “static” messing up sensor signals.
• Weatherproof to the Core: Rubberized insulation that shrugs off rain, snow, and road salt, with sealed connectors that keep moisture out—critical for rear bumpers, which take the brunt of slush and debris.
• Locking Connectors: Gold-plated terminals with a mechanical “click” that stays tight, even over years of driving on rough roads. No more wiggling wires to fix a sensor.
• Model S-Specific Fit: Engineered only for 2016-2021 Model S front radar bumpers, with pre-measured lengths that tuck cleanly behind the rear bumper. No extra slack, no missing mounting points—just a plug-and-play install.

What You Get (And Why It’s Worth It)

• 1x Rear Wiring Harness (1004421-04-T)
• A step-by-step guide with photos showing how it routes behind the rear bumper (no more guessing which clip holds which wire)
• 2-year warranty covering defects—we stand behind its ability to keep front and rear systems talking.