What is the best way to add imobilizer to 91-96 nsx

socalx · 25 February 2017

A friend of mine's 1997 integra type r (no imobilizer) was recently stolen and recovered stripped due to how easy it was to defeat the ignition.

This has me thinking on what options exist to add an imobilizer chip type system to the nsx (pre 97) so the car cannot be taken by simply forcefully defeating the key. I'm not looking to add an alarm (don't like the aftermarket alarms and want to keep this car stock and simple) and am fine with the oem keyless entry of my 1993. I also realize that with a flatbed or tow truck anything can happen.

All I'm looking for is the simplest and most non invasive way to prevent the car from being taken by forceful override of the ignition switch or hot wiring

The solution could be as simple as someone telling me the best old school way to simply install an ignition kill switch (crude but solves the issue in a simple way but is manual). Or hoping perhaps it could be even more creative by doing something automated that uses oem chip type technology added creatively in series with ignition Maybe a chip in the oem keyfob (I like the titanium key) that must be placed near a sensor added in in order to start the car)

Let's see if we can get some ideas here

Thanks

Old Guy · 26 February 2017

Every NSX has a starter cut relay which is tied into the security system. The starter cut relay blocks the starter motor from engaging if the security system is armed. So you already have a version of your ignition kill switch. Its not too hard to defeat the system by-passing the cut relay - if you know where the cut relay is located.

The immobilizer in the later NSXs is more theft resistant because the code is stored on an add-in card (separate from the immobilizer antenna and the immobilizer control unit) which is inside the ECU case. The service manual sets out the test procedures using the special Honda tester, it does not really describe the system so some interpretation is involved in reading the service manual. If the immobilizer control unit reads the key code and passes the code to the ECU and the ECU compares the codes and grants the permissive to start the engine, that is moderately secure since in order to do a hard wire by-pass of the immobilizer, you need to get inside the ECU - which is time consuming. If the immobilizer control unit reads the key and then reads the code in the ECU, compares them and then grants the start permissive, that is less secure because the control unit is outside the ECU and easier to by-pass. However, nobody probably does that type of by-pass. On the older immobilizers there are a limited number of codes so they are always subject to a brute force type of password attack (repeatedly blasting key codes until one of them takes). The more convenient way of stealing late model cars appears to use the code learning function accessible through the OBDII port where they reprogram the ECU to accept a new key code and then drive away. The NSX's key code learning function is a lot more kludgy than that, so might be immune to that type of attack.

You could do an add-on immobilizer based upon using an RFID or a near field technology (both of which can be grabbed). Ultimately, any add on immobilizer function will suffer from the problem of being by-passable once the thief has found the point where the immobilizer permissive is tied into the vehicle wiring system. However, that takes time which is all that it may take to discourage a thief.

Perhaps a steering wheel club is the answer?

Jinks · 26 February 2017

Detachable steering wheel........

shinjyo · 28 April 2017

Old Guy said:
Every NSX has a starter cut relay which is tied into the security system. The starter cut relay blocks the starter motor from engaging if the security system is armed. So you already have a version of your ignition kill switch. Its not too hard to defeat the system by-passing the cut relay - if you know where the cut relay is located.

The immobilizer in the later NSXs is more theft resistant because the code is stored on an add-in card (separate from the immobilizer antenna and the immobilizer control unit) which is inside the ECU case. The service manual sets out the test procedures using the special Honda tester, it does not really describe the system so some interpretation is involved in reading the service manual. If the immobilizer control unit reads the key code and passes the code to the ECU and the ECU compares the codes and grants the permissive to start the engine, that is moderately secure since in order to do a hard wire by-pass of the immobilizer, you need to get inside the ECU - which is time consuming. If the immobilizer control unit reads the key and then reads the code in the ECU, compares them and then grants the start permissive, that is less secure because the control unit is outside the ECU and easier to by-pass. However, nobody probably does that type of by-pass. On the older immobilizers there are a limited number of codes so they are always subject to a brute force type of password attack (repeatedly blasting key codes until one of them takes). The more convenient way of stealing late model cars appears to use the code learning function accessible through the OBDII port where they reprogram the ECU to accept a new key code and then drive away. The NSX's key code learning function is a lot more kludgy than that, so might be immune to that type of attack.

You could do an add-on immobilizer based upon using an RFID or a near field technology (both of which can be grabbed). Ultimately, any add on immobilizer function will suffer from the problem of being by-passable once the thief has found the point where the immobilizer permissive is tied into the vehicle wiring system. However, that takes time which is all that it may take to discourage a thief.

Perhaps a steering wheel club is the answer?

Does start cut replay apply to my 95 without keyless entry? I use keys to lock and unlock, not a remote. I am afraid that someone will use oldschool ruler to unlock through my window or something.

Old Guy · 29 April 2017

Yes - every NSX from 1991 to end of production has the cut relay. If nobody has messed with the car wiring or disabled the relay, the cut relay will get energized when the security system is armed. If the little red light by the driver door lock knob is blinking, then the cut relay should be engaged.

Note that the starter cut relay is only in the starter motor circuit. It does not immobilize the ECU. If a thief can defeat the ignition lock (by brute force or whatever), they can by-pass the starter cut relay from inside the engine compartment by jumping the starter motor solenoid. But, that is a problem common to just about every aftermarket security system. The aftermarket security system immobilizers are starter motor immobilizers, not ECU immobilizers.

MaxGeek · 29 April 2017

I'm also interested in adding an aftermarket immobilizer. I've seen some bluetooth/smart phone products like iBlue and Ernest, but there aren't any real reviews of them out their. iBlue's app has questionable reviews in terms of legitimacy and Ernest didn't have any app reviews. I'd be fine with a basic immobilizer too.

warrenw · 30 April 2017

If they really want your car, no immobilizer will stop them. Serious thieves use tow trucks. Good insurance with a valued appraisal is your best defense.

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MaxGeek · 2 May 2017

You definitely can't stop everyone, but if you can stop simple thieves with an inexpensive immobilizer why not. Even GPS tracking devices are cheap and easy to install.

Old Guy · 2 May 2017

All NSXs have a starter circuit immobilizer tied into the security system already. The later models have a second level of theft prevention associated with the coded immobilizer in the ECU which is completely separate from the starter circuit immobilizer. So, you have an 'inexpensive' immobilizer already.

The OEM keyless entry weakens the security of the starter circuit immobilizer because it uses a simple fixed code in the radio transmitter to disarm the system. That code can be easy to capture. The aftermarket systems and the blue tooth thingies may be more resistant; but, ultimately I expect are all subject to capture if the thief is nearby. This is an occasion where long transmission range on your remote is a bad thing. If you want to improve the security of your starter immobilizer, don't use a keyless entry system of any kind.

Mac Attack · 2 May 2017

socalx said:
I also realize that with a flatbed or tow truck anything can happen.

All I'm looking for is the simplest and most non invasive way to prevent the car from being taken by forceful override of the ignition switch or hot wiring

The solution could be as simple as someone telling me the best old school way to simply install an ignition kill switch (crude but solves the issue in a simple way but is manual). Or hoping perhaps it could be even more creative by doing something automated that uses oem chip type technology added creatively in series with ignition Maybe a chip in the oem keyfob (I like the titanium key) that must be placed near a sensor added in in order to start the car)

Let's see if we can get some ideas here

Thanks

If I have to park someplace overnight or leave the home for an extended period I just pull the small 25A minifuse out of my custom fuel pump wiring setup. It's simple, fast, and doesn't interrupt power for those using the OEM ECU.

What is the best way to add imobilizer to 91-96 nsx

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