5G: dealing with new keys and ignition cylinder

cdent · Post by **cdent** » Wed Dec 09, 2015 4:25 pm

My well loved but a bit beat up 5G prelude needs a new ignition cylinder and keys because both the barrel of the cylinder and the key are very worn, causing intermittent stalls and difficulty starting if I don't have the key in exactly the right place and the cylinder doesn't stay exactly still. Also it is possible to pull the key out when the cylinder is any position (and the car continues to run).

I only have the one key (that's what it came with when I bought it).

This problem has been present for a couple years now but of late has become bad enough that I'd like to fix it. From what I can discern Honda no longer produces the cylinders and even if they did they would be expensive. I've found a full set of locks and cylinders parted out, with keys.

If I get that, what are my options for dealing with the immobiliser? Can I retrain it to the new keyset? If I keep the old key near the ignition can I just carry on and not worry or will the two keys in proximity cause confusion and trouble? Can the old key be copied into the new keys?

Thanks for any input. I'd like to keep this lovely car running a while longer.

Lankysod07 · Post by **Lankysod07** » Wed Dec 09, 2015 4:46 pm

I restore Mazda Mx5's in the summer and a common issue ive come across with these are the ECU's get wet or the immob circuit boards burn out.

In this case you have to replace the ECU/Immob box/ignition cylinder and the keys. (But you can get round half of this by taping the old key with the immob chip inside to the round plastic immob receiver).

However, you should be able to keep the same ECU and immob but change the ignition cylinder and keys, then take the small plastic trim (immob receiver) that goes round the ignition cylinder where the key enter's from the old one igniton and tape your old key to it and hide it under the dash out of sight.

Then use your new key and it should be fine aslong as there not too close to each other to cause confusion!

cdent · Post by **cdent** » Thu Dec 10, 2015 10:23 am

Hey, thanks for the info, very helpful.

Anybody care to comment on my options for making the new keys work with the old receiver?

'92 Si VTEC · Post by **jjmartin349571** » Thu Dec 10, 2015 12:32 pm

If you have the red key then a decent auto locksmith should be able to code new keys to your car, as long as they have a transponder chip in.

I wouldn't go taping keys inside the dash to defeat the immobiliser personally.

Lankysod07 · Post by **Lankysod07** » Thu Dec 10, 2015 4:03 pm

Yeah it does leave your car essentially with a deactivated immobiliser as the key is always taped there!

cdent · Post by **cdent** » Fri Dec 11, 2015 5:06 pm

For an update: I've replaced the lock cylinder and discovered that in order for the key transponders to work with the immobiliser halo the key has to be pretty much in the halo and the halo assembly is a bit structural so swapped the old transponder into the new key. Ugly surgery on the keys but it works.

cdent · Post by **cdent** » Sat Jan 02, 2016 3:24 pm

Latest update: I got new cloned transponder keys so I wasn't carrying around sliced open keys but things still weren't working perfectly. Replacing the completely worn out key cylinder certainly helped but now I've also replaced the ignition switch (which shows some heat damage) and that's improved the situation some more. Based on what I've read the ignition switch was probably the original problem and the worn cylinder made it worse.

Now I need to purge the power steering fluid. It make cavitation sounds every now and again. Presumably it got the wrong kind of fluid in there at some point.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jan 12, 2016 10:41 pm

Glad to read you've got that problem sorted.

It reminds me though, something I've never understood... Can someone explain the red key to me please... They give it to you but say never to use it to start the car, right? So in that case... Presumably it must send out a code that clears whatever is stored in the immobilizer? So how does it help with programming a new key?

'92 Si VTEC · Post by **jjmartin349571** » Tue Jan 12, 2016 11:09 pm

I think it's a social experiment

mercutio · Post by **mercutio** » Wed Jan 13, 2016 5:24 pm

i think if you ever lose your key or have it stolen you can get a key cut with a different code and use the red key to reset the immobiliser to accept a new code???