Rywire B Swap Adapter Harness for 88-91 Civic/CRX

Rywire B-Swap Adapter Harness - 1988-1991 Honda Civic / CRX

Dropping a B-series into your EF Civic or CRX? The motor's the fun part. The wiring is where a lot of budget swaps turn into a headache, because your B16 or B18 engine harness doesn't just plug into a chassis that came with a D-series from the factory. That's exactly what this Rywire adapter harness fixes. It plugs in between your B-series engine harness and your car's existing wiring, so you get everything talking to each other without cutting, splicing, or depinning connectors one wire at a time. It's the clean, budget-friendly way to handle the electrical side of an EF B-swap and actually get the car running right.

What This Harness Actually Does

Let's be clear about what you're buying, because adapter harnesses get misunderstood. This isn't a full engine harness, it's the bridge between two harnesses that weren't built to talk to each other. On one side it connects to your B-series engine harness, on the other it plugs into the factory chassis wiring in your EF, and it sorts out the differences in between. So instead of spending a weekend with a wiring diagram, a depin tool, and a roll of tape hoping you didn't mix up a wire, you plug the adapter in and move on. Rywire builds these to keep your car's electrical systems intact and working the way they should, which matters when the alternative is hacking up your original harness and hoping for the best.

Pick The Right Variant For Your Car (This Part Matters)

Read this before you order, because this harness comes in three versions and they're not interchangeable. Honda wired these chassis differently depending on the trim and the year, so you've got to match your car to the right one. Here's how it breaks down:

• 1988-1991 Civic/CRX Si, HF, or EX: if you've got one of the higher trims, this single version covers all four years.
• 1988-1989 Civic/CRX DX or STD: for the early base-trim cars.
• 1990-1991 Civic/CRX DX or STD: for the later base-trim cars, which got slightly different wiring than the 88-89.

So the move is simple: figure out your trim first (Si/HF/EX versus DX/STD), then your year if you're on a DX or STD, and grab the matching variant. Get that right and the harness plugs in like it should. Order the wrong one and it won't line up, so take the extra minute to confirm before you buy.

Why Budget Builders Reach For This

The EF B-swap is one of the all-time great budget builds, a light little chassis with a screaming VTEC motor in it, and the whole point is doing it without spending Civic-Type-R money. This harness fits right into that philosophy. It saves you the labor and the guesswork of rewiring everything by hand, it keeps your factory wiring usable instead of cutting it up, and it gets you to a running, reliable swap faster. For most people building one of these, that's exactly the trade you want: spend a little on the right adapter, save yourself a whole lot of frustration.

What You Get

• Rywire B-swap adapter harness for the 1988-1991 Honda Civic and CRX (EF chassis)
• Connects a B-series engine harness to your factory EF chassis wiring
• No cutting, splicing, or depinning your original harness required
• Chassis- and trim-specific design for a correct fit
• Keeps your factory electrical systems intact
• Available in three variants by trim and year (choose the one that matches your car)

Fits These Cars

• 1988-1991 Honda Civic/CRX Si, HF, EX (one variant covers all years)
• 1988-1989 Honda Civic/CRX DX, STD (early variant)
• 1990-1991 Honda Civic/CRX DX, STD (later variant)

Note: Rywire B-series swap adapter harness for the 1988-1991 Honda Civic and CRX (EF chassis). It connects a B-series engine harness to the factory chassis wiring, letting you run a B-series swap without cutting, splicing, or depinning your original harness. Offered in three variants to match how Honda wired these cars: 1988-1991 Civic/CRX Si/HF/EX (one harness for all years), 1988-1989 Civic/CRX DX/STD, and 1990-1991 Civic/CRX DX/STD. Confirm your trim and year and select the matching variant before ordering, as the versions are not interchangeable. One adapter harness per order.