1989–1999 GM 3.1 / 3100 Harness + Tuned ECM Package — No Core Required

1989–1999 GM 3.1 / 3100 Harness + Tuned ECM Package

Complete simplified wiring package for 1989–1999 GM 3.1 and 3100 builds — tuned ECM included and no core required.

This LMMF package is built for the older GM 3.1 and 3100 platform, covering 1989–1994 3.1 flat-top engines, 1995 3100 engines, and 1996–1999 3100 engines. It gives you a clean, dependable simplified wiring solution without chasing down parts or sending in an ECM core.

Kept in stock • Usually ships within 1–2 business days • Tuned ECM included • No core required • Injector harness included

Fits

• 1989–1994 GM 3.1 flat-top engine applications
• 1995 GM 3100 engine applications
• 1996–1999 GM 3100 engine applications
• Demolition derby, race, off-road, and simplified engine-swap builds

What’s Included

• Professionally built simplified standalone engine harness
• Tuned ECM matched to the package
• Injector harness for 1989–1995 3.1 / 3100 applications
• All-new wiring, new connectors, and quality components

Injector Harness Details

The included injector harness is used for 1989–1994 3.1 flat-top and 1995 3100 engine applications. It is included with every package, but it is not required for 1996–1999 3100 engines.

What This ECM Includes

• Security / VATS delete
• Raised rev limiter
• Fueling adjustments for derby, race, and off-road use
• Timing adjustments
• Adjusted temperature parameters
• Unused sensors removed to reduce unwanted shutdown and fault issues
• MAF delete

No Core Required

Your tuned ECM is included. You do not need to send in an ECM core or return one after purchase.

We Buy Cores

LMMF buys compatible ECM cores separately. Contact us before sending one in so we can confirm compatibility and provide current purchase details.

In Stock & Fast Shipping

These complete harness and ECM packages are kept in stock and usually ship within 1–2 business days.

Before You Order

• Confirm whether your engine is a 1989–1994 3.1 flat-top, a 1995 3100, or a 1996–1999 3100.
• The included injector harness is needed for 1989–1995 applications and is not needed for 1996–1999 3100 engines.
• This is not the correct package for 2000–2005 3100/3400 applications.
• For newer 1996–2005 3100/3400 applications, shop the LMMF 1996–2005 GM 3100/3400 Harness + Tuned ECM Package.
• Contact LMMF before ordering if you are unsure about engine year, engine configuration, or vehicle compatibility.

Complete wiring. Included ECM. No core hassle. Plug it in and send it.

Off-road, race, engine-swap, and demolition derby use only. Not intended for emissions-controlled or street-driven vehicles.