Whether you use your vehicle mainly for racing or for city driving, an ECU conversion harness is a must-have. This part is essential because it helps interface your vehicle chassis with its newly swapped hybrid motor. It is important that it is always in good condition to ensure that it functions correctly. If you plan to change your worn-out stock harness with a new one, then you need to know how to do it properly. Or else, it could cause damage to your vehicle or your engine computer. The guide below might look tricky at first because of the color-coded connections that you need to plug in properly, but these codes also make it easier for you to install your harness.
Difficulty level: Moderate
What you'll need:
- Wrenches (socket and combination)
- Hand gloves
- Flash light
- Vice grips
- New ECU conversion harness
Step 1: Take out the battery, battery tray, and fuse box from your vehicle. Make sure to disconnect the negative connector before doing this. Also, be careful to not let the positive terminal touch any metal part of your vehicle.
Step 2: Look for the factory ECU under the dash at the passenger side. You can refer to your vehicle's owner's manual to know the exact location of this part. Remove it as well.
Step 3: Remove the factory engine harness from the engine bay under the dash. You will find two pieces of 10 mm bolts under the battery tray, which holds the harness in place. Remove this plate or grommet to reuse with your replacement engine harness.
Step 4: Route the replacement engine harness through the firewall located at the passenger side of your vehicle, using the factory grommet.
Step 5: Run the harness along the inside of the floor, near the firewall. Make sure that you have all of the connectors in one area only.
Step 6: Next, connect the green wire from your harness back to the dash harness.
Step 7: Connect the other wire from your harness to the connector on the engine harness.
Step 8: Insert connector A and B on your new engine harness into your ECU.
Step 9: Insert the white E plug, which you can find on your conversion harness, into the ECU.
Step 10: Look for the gray 10 pin connector on the shock tower at the driver side.
Step 11: Pull the connector carefully through the firewall.
Step 12: Connect the other end of your new harness.
It would take you at least an hour to install your new ECU conversion harness. It would be better to do the repair in a well-lit area to ensure that the wires are connected properly. If you experience any problem starting your vehicle after installation, just check if you have plugged the wires correctly. If it still won't work after a few tries, you might consider taking your vehicle to an expert to have it checked or fixed, especially if you do not have any experience in installing the harness.