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Simple Wiring for Louder Horns
The GrimmSpeed Hella Horn Wiring Harness gives 2002 to 2014 Subaru WRX and STI owners a straightforward way to wire up aftermarket Hella horns without splicing into the factory harness. GRMGRM040005 is built with automotive grade 16 gauge wire to minimize resistance and deliver maximum volume from the new horns, along with heat shrink crimp on terminals for a dependable connection. Protective wire sleeving keeps GRMGRM040005 looking clean while shielding it from abrasion and stress in the engine bay. Designed as a true plug and play upgrade, it connects directly to the OEM harness and installs in minutes alongside a set of Hella horns and a mounting bracket like the GrimmSpeed BroTie.
Key Features
- Automotive grade 16 gauge wire for minimal resistance and maximum volume
- Heat shrink, crimp on terminals for a dependable connection
- Protective wire sleeving for a clean look and added durability
- Plug and play design that installs and uninstalls in seconds
- Compatible with the OEM horn harness connector
- Can be adapted for use with a more complex relay harness
Fitment
| Year | Make | Model |
|---|---|---|
| 2002-2014 | Subaru | WRX |
| 2004-2014 | Subaru | WRX STI |
Specifications
| Detail | Value |
|---|---|
| SKU | GRMGRM040005 |
| Manufacturer Part Number | 040005 |
| Wire Gauge | 16ga Automotive Grade |
| Terminal Type | Heat Shrink Crimp On |
| Fitment | 2002-2014 Subaru WRX, 2004-2014 Subaru STI |
| UPC | Not published by manufacturer |
What's Included
- 1 GrimmSpeed Hella Horn Wiring Harness (GRMGRM040005)
About GrimmSpeed
GrimmSpeed is a Minnesota based performance manufacturer that focuses on practical, reliable upgrades for Subaru vehicles. GRMGRM040005 is part of their approach to making common upgrades, like aftermarket horns, easy to wire correctly the first time.
Related Parts
- GrimmSpeed 2015+ WRX/STI Hella Horn Wiring Harness
- GrimmSpeed 08-18 Subaru WRX/STI Lightweight Battery Tie Down
FAQ
What is the 040005?The 040005 is the GrimmSpeed Hella Horn Wiring Harness built for 2002 to 2014 Subaru WRX and 2004 to 2014 Subaru STI models.
Which vehicles does GRMGRM040005 fit?It fits 2002 to 2014 Subaru WRX and 2004 to 2014 Subaru STI models with the factory horn wiring connector.
Does GRMGRM040005 include a relay?No, the standard harness skips the relay since GrimmSpeed testing found it added complexity without a meaningful volume benefit.
Can I upgrade to a relay setup later?Yes, GRMGRM040005 can be adapted to work with a more complex relay based wiring setup.
Do I need to cut or splice any factory wiring?No, it plugs directly into the factory OEM horn connector without any cutting or splicing.
What wire gauge does this harness use?It uses automotive grade 16 gauge wire for minimal resistance and strong volume output.
Does this listing include a mounting bracket for the horns?No, this is the wiring harness only. A bracket such as the GrimmSpeed BroTie is sold separately.
How long does the install typically take?Once the horns and bracket are mounted, wiring GRMGRM040005 usually takes just a few minutes.
Install Instructions
- Disconnect the factory horn connector from the OEM wiring harness.
- Mount the aftermarket Hella horns using a bracket such as the GrimmSpeed BroTie.
- Connect the female terminals of GRMGRM040005 to the spade connectors on each horn.
- Plug the male terminal end into the factory OEM harness connector.
- Secure the wiring away from moving parts and sharp edges.
- Test the horns before reinstalling the front bumper or trim panels.
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