LS2-SA Labels Braided_Loom 53_Caddy_eng5.jpg FuseBox_Close



Modification of Stock Engine Harness

If you’ve acquired an LT1, LSx Gen 3 or 4, or Gen 5 (LT1, L83, L86, L8T) style engine that came with a wiring harness on it, and you feel that the length of the harness to the ECU, and the look of the harness will work fine for your project, then we can simply modify it to be a stand alone engine management harness. This means that we take the harness that you supply, and add all of the required fuses and relays in a simple relay center that mounts near the ECU under the hood. The relay center contains all of the fuses for the harness and any relays that are needed such as ignition power, starter, and Fuel pump. We remove any unnecessary wiring such as emissions controls and O2 sensors that may not be used.
This harness modification does not eliminate VATS or emissions controls in the ECU. This must be done in the programming, or else a VATS module needs to be installed in the harness for an additional charge.

Programming is also available to take care of setting up the ECU to work in your project, eliminating such things as emissions controls, O2 sensors, air pump, VATS, etc.

Example of LT1 harness modified to stand alone shown below.



Stage 1 Engine Harness Modification  $325.00   Gen V – $425.00
Includes Basic relays and fuses to make the engine run.
(i.e. Fuel Pump, Starter, Ignition Power relays, and fuses for engine)

Stage 2 Engine Harness Modification  $400.00   Gen V – $500.00
Adds A/C and Electric Fan wiring as well as all needed relays and fuses.
(Can be wired for computer control or manual switch for fans)

LS1 Computer Programs starting at $175

LT1 Computer Programs starting at $315
VATS Bypass module added for additional $35 (Not needed with programming)


The Fuses and Relays for custom harnesses can come one of 2 ways. Either the standard separation of all relays where they are mounted in the engine compartment usually on the firewall or fender, or a compact OEM looking Fuse/Relay center where all of the components are in one central location. The fuse/relay center style is shown below. All of the fuses and relays are labeled on the underside of the covers just like a factory vehicle.



All of the Engine Management Harnesses come with wires that need to be wired in to the vehicle. Any wires that are loose are labeled and instructions are always included describing where the wires need to be connected.
These wires may include:

  • A simple 12V switched source
  • Check Engine Light
  • Speedometer
  • Tachometer
  • A/C Compressor
  • Park/Neutral for ECM
  • Starter relay signal
  • Fuel Pump Power
  • Brake switch signal


Additional information

Weight 8 lbs
Dimensions 12 × 12 × 8 in
Harness options

Basic Stand-Alone, Add Fans & A/C, Gen V Basic Stand-Alone, Gen V Fans & A/C

Loom option

Stock corrugated plastic, Braided Loom ($75)


There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.

You may also like…