OEM Honda Wire Colors
Built Around 2002 to 2004 RSX Wiring
Machine Tested Pin to Pin
Included Adapter Harnesses Allow You to Upgrade without Cutting
This is a complete engine harness built around 2002-2004 RSX (DC5) and K20A2 wiring, and it sits in a gap nobody was filling. On one side you've got budget replacement harnesses with histories nobody can account for. On the other, full motorsports harnesses that cost more than the engine going in. This is the one in between: clean tucked routing, factory Honda wire colors so you can actually trace a circuit, and machine testing on every single harness before it ships.
Our first successful product was a K-swap conversion harness, and wiring has been part of what we do ever since. What shaped this design was years of helping customers trace swap problems back to the same handful of causes: wiring errors, and harnesses nobody could vouch for.
So everything here comes from that experience. OEM Honda wire colors so a technician can follow a service manual. Removable injector and VSS adapters so you're never cutting into the main loom. K24 crank and knock sensor connectors in the box. Three spare circuits through C101 for whatever you add later. And a machine test against the production wiring map before it leaves the building.
The branches take a tidier path through the bay and tie down at factory mounting locations, which does two things. It looks right with the hood up, and more importantly it stops the harness moving around, which is what causes rubbing and eventual wear-through.
The wire colors and stripe patterns follow the corresponding Honda circuits. That sounds minor until you're troubleshooting at midnight and can pull up a factory service manual and trace exactly what you're holding. A harness in generic colors leaves you guessing.
This is the design decision we're proudest of. The injector and VSS connections live on removable adapter harnesses that plug into the main loom rather than being wired into it.
It ships with an injector adapter for 2002-2004 RSX Type-S and K20A2-style injector connectors, the ones people call Honda OBD2 injector clips, plus a VSS adapter for the K20A2 final-drive-driven speed sensor. If your injectors or transmission use different connectors, optional adapters swap right in. No cutting, no depinning, no repinning the main harness.
That matters over the life of a build, because setups change. A harness that can change with them is worth a lot more than one you have to modify with a razor blade.
The K24 connectors are in the box and the change is straightforward. Depin the terminals from the K20 crank and knock sensor connectors, repin them into the included K24 connectors during installation, and you're set. Careful work, but no cutting.
Wiring is where swaps go wrong, so here's everything worth confirming up front. If any of it is unclear for your setup, email our tech team and we'll sort it out with you.
You probably still need a conversion harness. This is the engine harness, connecting your sensors, injectors, coils, alternator, and ECU. A chassis conversion harness is what ties that RSX-style wiring into your car's factory chassis wiring. Unless your car already has chassis wiring built to accept a factory 02-04 RSX engine harness, you need both.
Your engine code alone doesn't confirm fitment. It depends on the engine code, crank and knock sensor connections, throttle setup, injector connectors, transmission VSS, ECU, and chassis wiring together. And to be direct about a common assumption: K-Pro compatibility does not confirm fitment. That names a tuning platform, not a complete engine, transmission, and wiring combination.
Drive-by-cable only. This harness has circuits for a cable throttle body using a Honda-style TPS. There's no drive-by-wire control built in, so a DBW engine won't work with it.
Wideband ECUs only. It's designed to work with a US or JDM spec ECU using a factory Denso wideband O2 sensor. Do not use it with a UK spec narrowband ECU.
Not for K20C or direct-injected K24.
One note on the US spec VTEC oil pressure switch. This harness doesn't support it, because most engines don't have it and most don't need it. You'll disable that sensor in your tuning software, and it has no effect on VTEC operation.
The installation guide has an engine-by-engine compatibility reference that spells out what your specific setup needs. If you'd rather have us check, send tech support your engine code, transmission and VSS type, ECU, throttle body, and chassis before you order.
The main harness uses AVSS thin-wall stranded bare copper automotive wire built to JASO D611, with 0.5mm² on signal circuits and 1.25mm² on grounds. The ECU connection is a three-piece 86-way OEM-pattern plug set.
Every completed harness is machine tested against the production pin-to-pin wiring map, checking for incorrect connections, open circuits, and shorts. That's the part that matters most, because a wiring fault caught on a test bench costs nothing, and one caught with the engine in the car costs a weekend.
Injectors and the vehicle speed sensor are not included.
Do I still need a K-swap conversion harness?
Almost certainly. This engine harness connects your engine sensors, injectors, coils, alternator, and ECU. The conversion harness connects that RSX-style wiring to your car's factory chassis wiring. You only skip it if your car already has chassis wiring made to accept a factory 02-04 RSX engine harness.
Does it work with both K20 and K24?
Yes, on supported combinations built around 02-04 RSX-style wiring. A K24 needs the included connectors swapped in, depin from the K20 crank and knock connectors and repin into the K24 ones. The installation guide covers what else your specific engine requires.
What can I change later without cutting?
The injector and VSS connections. Both live on removable adapter harnesses, so if your injectors or transmission change, you swap the adapter rather than modifying the main loom.
Does K-Pro compatibility mean it fits?
No. That's a tuning platform, not a wiring specification. Match your engine sensors, throttle setup, transmission VSS, injector connections, ECU, and chassis wiring against the installation guide before ordering.
Will it work with a narrowband O2 sensor or ECU?
No. It's built for a US or JDM spec ECU running a factory Denso wideband O2 sensor. Don't use it with a UK spec narrowband ECU.
Will it work with drive-by-wire?
No. The harness only has circuits for a cable throttle body with a Honda-style TPS. There's no DBW control in it.
What does the machine test actually check?
It compares the finished harness against the production pin-to-pin wiring map and flags incorrect connections, open circuits, and shorts.
Need help confirming fitment, choosing an injector or VSS adapter, or working through the K24 repin? Our tech support team is an email away and can tell you exactly which parts your combination needs. The harness carries a one-year warranty.
This is for the builder who wants a properly made engine harness without going full Mil-spec, and who'd rather have factory wire colors and a test report than save a hundred dollars on something with an unknown past. Wiring either disappears into the background or ruins your year, and there's not much in between. Send us your combination if there's any doubt, order the right parts, and do it once.
Type: complete K-series engine harness, built around 2002-2004 RSX (DC5) / K20A2 wiring.
Supports: K20 and K24 swaps using K20A2-style sensors, controls, and a compatible ECU.
Not for: K20C, direct-injected K24, drive-by-wire, or narrowband ECUs.
Includes: injector and VSS adapter harnesses, K24 crank and knock sensor connectors, three spare C101 circuits, and harness ties.
Note: a chassis conversion harness is required unless your car already accepts a factory RSX engine harness. Does not support the US spec VTEC oil pressure switch.
Warranty: one year.
