Speartech STE-LT4-8L90 Gen 5 LT4 8L90E Standalone Wiring Harness Kit

The Speartech STE-LT4-8L90 is a complete Gen 5 LT4 / 8L90E standalone wiring harness package engineered for engine swap builds using the supercharged 6.2L LT4 paired with the GM 8L90 8-speed automatic transmission. Built to order, each harness is custom-assembled and test-run on an in-house LT4/8L90 builder engine to verify proper functionality before shipping.

This plug-and-play harness system delivers full-function, closed-loop engine and transmission control, giving builders everything needed to bring a Gen 5 LT4 powertrain to life in a custom application. The standard trunk length of 3.5 feet is measured from the rear of the engine to the ECM mounting location, optimized for cabin-area installation away from moisture and heat.

Kit Includes:

• Engine Main Harness
• Transmission Main Harness
• Engine ECU (programmed)
• Transmission TCM
• EVAP Canister
• Post and Pre-Cat Oxygen Sensors
• Drive-By-Wire (DBW) Throttle Pedal
• Complete printed installation instructions

Key Features:

• Every wire individually labeled for easy installation and troubleshooting
• Integrated OBD2 port with check engine light support for on-board diagnostics
• High-temp woven harness covering for durability and a clean, show-quality appearance
• Built for full-function, closed-loop control (non-emissions configuration — no post-cat O2s, purge canister, or fuel tank EVAP interface)
• Custom trunk length available upon request

Speartech is a specialist in GM LS and LT engine swap wiring harnesses, backed by over two decades of GM engineering experience. The STE-LT4-8L90 is legal for sale and use on uncontrolled (non-emissions-controlled) vehicles only.