Main Relay Kill Switch


The problem with a fuel pump kill switch is that it's easy to bypass and run battery power directly to the fuel pump. It's easy to determine when the fuel pump isn't powered up because you can hear it fail to prime. Fuel pump kills are common and widely known in part because of my write-ups several years ago but also because too many people rely solely on a cheap switch as their only security. As a result, fuel pump kills are no longer a reliable way to prevent your car from being stolen.

The PGM-FI Main Relay controls the Fuel Injectors, the Fuel Pump, the O2 sensor, the Alternator, and the Vehicle Speed Sensor. Thieves mistakenly diagnose it as a fuel kill and waste time bypassing the pump to no avail.

Tools and Parts

How To Kill the PGM-FI Main Relay

The Main Relay has a black, low current ground wire. If you put your switch on this one wire, you can kill the entire relay. Some of Hondas have two wires and you will need to cut both and treat them as one wire.

This is optional but to keep the wiring stock and make this process easily reversible, I went to the junkyard and cut a main relay harness. I then de-pinned the black wire to use for my kill switch so I could tuck my original black wire away.

This is what the main relay looks like on 94-01 Integras and 92-95 Civics and Del Sols. You can remove the 10mm bolt and unplug the harness using a flat blade screwdriver. For 96-00 Civics, follow this link to find your main relay: EK Kill Switch

Push the clips in on each side.

Pry the white clip up but don't completely remove it. You just need to free the black wire.

There's a little tab inside that you'll need to flatten down with a straight pick. Press on it while pulling on the wire.

If your car has two ground wires, you need to connect them together on the chassis side. Tape the connection and tuck the wires into the split loom.

Wire the Switch

Once you remove the stock wire you can tuck it into the factory loom. Pin your junkyard wire and extend it to your switch. If you're not using a junkyard wire then cut your factory wire and extend the relay side to your switch. Once you've decided where to mount your switch, you ground the switch's other pin using a ring terminal and a metal tapping screw or a factory bolt.

People have asked for a wiring diagram but it's literally two wires.

I wont give you an example of where to mount the switch because in the past I have found that many people will imitate it exactly.

Relocate Main Relay

To bypass your kill switch someone only needs to ground the main relay. So you'll need to hide it. You can extend all the wires and move it somewhere but for this write-up I'm just moving it up as high in the dash as it will reach.

You need to cut the tape to separate the main relay harness from the rest of the wires in the loom.

Then I bent this tab so that the bracket would be flat.

I removed the knee bolster so I could access this spot where I re-mounted the main relay. A thief can still get to it here but if you have an alarm they shouldn't be spending enough time under the dash to find it.

This is what it looks like relocated. After you put the knee bolster and dash panel back on it's invisible when looking up from below.

Loom and tape up the wires so that they look factory.

Make it Work with Remote Start

If you have remote start then you'll want to wire your negative status output wire (22 gauge blue/white on DEI alarms) to the black wire before the switch. You can remote start the car with the main relay kill switch active, but you have to deactivate it before you press the brake.