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91 NSX automatically locks 20 seconds after key removed

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17 March 2020
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I have owned my NSX 91 JDM for many years now and after the battery was replaced recently the doors have been autolocking when the key is removed and doors shut. Takes about 20 seconds from shutting door. This did not used to happen and I would like for it not to do that. I cannot find any info on google searches or NSX Prime and my manual is in Japanese :)

Any ideas appreciated
 
This might be your Keyless Entry System doing its job. The driver door switch isn't letting the KES know that you UNLOCKed your car.

If you do not have remote transmitters, then try unplugging the KES under the [passenger] glove box.

There are at least 2x types of KES for the 1991 JDM. One of them has a green 30P connector to a black steel box and the other is a 16P (18P?) grey connector to a banana-sized plastic box.

Either way, disconnect the connector from the box and post the result.
 
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Providing you have keyless entry, Drew has probably identified the source of the 10 second (that is the spec in the ETS manual) relock. That is a standard keyless function and normally occurs when you unlock the car using the remote; but, do not open the door. Unplugging the keyless module and seeing whether the relock goes away would be the quickest way to confirm that keyless module is the source of the relock. However, the module might not be the source of the problem. The module will initiate a relock if
- the driver's door or the front hood is not opened within 10 seconds of getting an unlock signal
- the switch in the ignition switch indicates that the key is still in the ignition switch (a rather confusing feature; but, that is what the ETM says)

To prevent the accidental unlocking of the doors and
leaving them unlocked, the keyless door lock control
unit will lock the doors automatically within 10 seconds
of an unlock transmission if the driver’s door or the front
compartment are not opened (switches closed) or if
the key is placed into the ignition (key switch closed).

So, you could have a problem with the door switch, hood switch or the ignition key switch which is confusing the keyless control module with an unexpected input sequence. You need the 1992 Electrical Trouble Shooting manual to sort this out because the service manual does not cover the keyless module.

If it is a door /hood/ key switch this is something that you might want to really fix other than patch it by unplugging the keyless module. Door switches in particular can be a sign of something going sideways with the latch. I think there is an Acura TSB covering problems with the switch in the latch which can cause problems with the keyless unit.

If you don't have a keyless entry unit, there should be no re lock function. However, you have a JDM spec car and while 95% of the car is pretty much the same as a North American spec car, JDM spec cars do have very specific differences - like the catalytic converter temperature alarms so perhaps this is a uniquely JDM feature.

As a final fling, since the problem started after a battery replacement check the condition of the battery post clamps to make sure that they are clean and tight. Failing battery post clamps can cause voltage issues and erratic operation of things like the keyless when the engine is not running to establish the vehicle voltage. NSX (Honda / Acura) battery post clamps are a bit notorious for being easily damaged by over tightening - they stretch and the clamp metal actually tears.
 
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Thanks for the replies Drew and Old Guy. I unpluged the security module (Green Plug) and the car no longer relocks. Central locking is working and car starts etc. I do have key remotes that I stopped using as were unreliable. Red light on remote key comes on (batteries changed) and I point at the receiver (rear of Door) but result is variable and not worth the hassle, I prefer the key. Thanks guys. What else does the security module do?
 
The IR system is absolute trash. There is a switch panel under the driver side that you might have accidentally changed too.

Your car is NOT equipped with a Security Control Unit. That didn't happen until the NA1-110 (AFAIK). You have a whole dealer add on security system and keyless that is quite crude.

I am trying to reverse engineer the IR system, but I dont have the parts that are in the door...so I'm guessing at the dis/arm protocol and I don't have the time anymore. There is no AG5 30P male wired connector so I have to build a PCB.

If you are looking for a RHD RF system, PM me.
 
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I am trying to reverse engineer the IR system, but I dont have the parts that are in the door...so I'm guessing and the dis/arm protocol and I don't have the time anymore. There is no AG5 30P male wired connector so I have to build a PCB.

If you are looking for a RHD RF system, PM me.
I'm in Auckland and have that stuff in my door but no remotes. Would happily remove it all if you want it
 
+1 on Drew's awesome RF remote locks system for RHD (or LHD if you are determined)

- adds confirmatory parking light flash and the remote trunk release that Honda was obviously thinking of (otherwise, just have a manual cable trunk release) and, of all things, separate lock/unlock buttons so you aren't guessing whether you just locked your car or unlocked it.
 
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