Metra Tuner Relocation Harness + GM Multi Kit - Clean OEM Integration

In this review the Metra 70-1857 tuner relocation harness bundled with the Metra 99-2011 GM multi kit is evaluated for installers who want to fit an aftermarket radio into 1990-up GM vehicles while retaining Bose amplifier functionality. The single biggest reason to buy this pair is the direct integration: the harness lets an installer relocate or bypass the factory tuner and interface cleanly with the Bose amplifier, while the multi kit secures single DIN or double DIN units for a factory-like installation. It is a practical choice for DIY enthusiasts and professional installers who prioritize compatibility and a tidy install.

Key Features

• Tuner bypass harness: provides a 17 ft long connection that eliminates the factory tuner and allows the aftermarket radio to interface with the vehicle's Bose amplifier.
• Bose amplifier integration: maintains preamp and speaker-level connections so the vehicle amplifier continues to power speakers without losing audio functionality.
• Multi kit fit: secures both single DIN and double DIN radios for 1990 and newer GM vehicles, helping achieve a factory-look dash installation.
• Power and preamp connections: plugs into the car harness at the radio location to simplify wiring and reduce the need for cutting stock wires.
• Made in USA multi kit: the multi kit is manufactured in the USA and ships in a compact package, offering reliability in components and mounting hardware.

Who It's For

This bundle is aimed at car audio installers and experienced DIYers who are upgrading GM dashboards and need to preserve the vehicle's Bose amplifier while using an aftermarket head unit. It suits projects where maintaining factory amplifier power and preamp outputs is important for speaker performance.

It is less appropriate for vehicles that do not use Bose amplifiers or for users who expect a plug-and-play radio with every adapter included; some vehicles may require additional adapters or trimming for perfect fit, and customers sensitive to possible wiring noise should be prepared to test ground and routing to minimize engine or electrical interference.

Pros & Cons

Pros

• Preserves Bose amplifier function so speakers remain amplifier-driven with an aftermarket radio.
• 17 ft harness length offers flexibility in routing and allows relocating the tuner where needed.
• Multi kit secures both single DIN and double DIN radios for a neat, factory-style finish.
• Many customers report easy installation and solid build quality for the harness and kit.

Cons

• Wire length feedback is mixed; some users find the harness very long while others worry about excess wiring management.
• There are reports from some customers of noticeable noise if grounding or routing is not optimized.

Specifications

Bundle components	Metra 70-1857 harness and Metra 99-2011 GM multi kit
Harness length	17 ft
Vehicle compatibility	Select GM vehicles 1990 and newer
Amplifier support	Bose amplifier integration, preamp and power pass-through
Multi kit dimensions	8.1 cm x 27.7 cm x 17.5 cm
Multi kit weight	0.5 lbs
Manufacturing	Harness manufactured in China; multi kit made in USA

Our Verdict

The Metra 70-1857 harness paired with the 99-2011 GM multi kit is a pragmatic, cost-effective solution for anyone installing an aftermarket radio in a GM vehicle equipped with a Bose amplifier. It preserves amplifier-driven speaker output and provides flexible routing with a long harness, making it good value for DIYers and pro installers who want a clean, factory-style result while accepting the need to manage wire length and ground routing to avoid occasional noise.

Frequently Asked Questions

Will this work with any GM vehicle?
It is designed for select GM vehicles 1990 and newer; compatibility depends on the vehicle's audio wiring and Bose amplifier setup, so confirm fit before purchase.

Does the harness keep the Bose amplifier functioning?
Yes, the harness is made to interface with the Bose amplifier, maintaining preamp and amplifier power so speakers remain amplifier-driven.

Are there installation issues to watch for?
Some users report mixed experience with harness length and occasional engine noise; careful routing, grounding, and trimming excess wire help avoid interference.