This blog post is written by Whitney using the notes she's acquired from answering Subaru wiring questions for customers for over seven years.
When it comes to adding new parts to a Subaru, there are a lot of important factors to consider. While the mechanical side is considered "legos," and for the most part, this is true, the wiring is full of nuances and differences. For example, the 2005 WRX differs from the 2006 WRX, and the 2006 WRX differs from the 2006 STi. Below are some notes and information I use to help customers assess if their projects are possible and what needs to be done.
My best advice is that if you're unsure or something doesn't align or plugin, slow down and research! The WORST thing you can do is panic, make hasty decisions, and then possibly ruin the new part you just purchased. (That might mean missing your tuning appointment the next day). Here are some basics "Do's" and "Dont's" for any Subaru project:
My other pro tip - make sure it will be street-legal in your state. The federal EPA writes emission laws, and it's up to each state to enforce those rules. If your state doesn't currently enforce the rules, that doesn't mean this will be the case forever. Before spending all your time, money, and effort on that dream Subaru project, make sure you can legally register it and drive it on the street.
1. Know what you have - What is the year and model of Subaru? Is it turbo or non-turbo? Is it an auto or manual? Knowing this information is critical to the success of a project. There are so many wiring differences between Subarus, and knowing what you have is the best place to start.
2. Which Engine Do I Have - We get this question from people doing engine swaps. Is it phase 1 or phase 2? Is it single or dual AVCS? Is it CANbus equipped? It's incredibly difficult to give sound advice without knowing the exact year and model the engine came from. Luckily we have a few resources to help figure out what engine you have:
3. CANbus - another critical part of any wiring project is considering whether CANbus will make an impact. As cars gain more advanced features like vehicle dynamics, screens, radio technology, etc., the car wiring gets more advanced. Doing conversions on CANbus-equipped cars can have many effects that people don't think of (for example, deleting the ABS may cause check engine lights and your DCCD to stop functioning). Below are the cars that are CANbus equipped and how that impacts engine swaps. Check out the blog links below for more detailed information on CANbus.
*CANBus engine into a CANbus-equipped chassis is a very difficult swap wiring-wise. We'd recommend just replacing the long block to keep the car alive.
4. Throttle Body Type - Drive by Cable (cable throttle) or Drive by Wire (electronic throttle). These two types have completely different ECUs, so knowing which throttle body your car has and which one the new engine has is important. Generally speaking, we utilize the ECU that matches the engine for a swap, so knowing if the chassis ECU and engine ECU are similar will dictate how many wiring changes there will need to be.
5. Immobilized - is the ECU you plan to utilize immobilized? The Immobilizer system is the built-in Subaru security system. If your car cranks for 3 seconds and then immediately dies, it's probably an immobilizer problem. Using an immobilized ECU is possible, but it comes with some extra wiring steps. Check out the blog post and charts below to learn more about the immobilizer system.
6. Transmissions - is your transmission auto or manual? Is it DCCD equipped? Does it have a built-in speed sensor or no speed sensor? When installing a new transmission, there are many things to consider wiring-wise. If you're going auto to manual, you have to add in reverse, neutral position, vss, starter, etc. If it's DCCD equipped, you'll want a DCCD Controller to get the most functionality. No speed sensor on your new transmission when the old one had one? You'll need a VSS replicator to get the speedometer working again (and fix that 4,000 RPM rev limit). Did your old transmission have two plugs, and now it only has a single four-pin plug? You'll need one of our transmission adapters to get the car running and driving. There's quite a bit of nuance to the wiring of a transmission swap, so check out the blog posts below.
7. When in doubt, remove variables! The more you add or change to a project between the car running, the more things you have to inspect to see if they are working. Check out this basic troubleshooting and diagnosis blog I wrote for some basic tips.