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Mike, Toyota Mechanic
Category: Toyota
Satisfied Customers: 39198
Experience:  Tech Expert
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Toyota Previa 1996 One key lost. I have the second key and

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Toyota Previa 1996 One key lost. I have the second key and it works fine also the separate alarm "clicker" works and opens and closes the doors etc, and disables the alarm system.
Went to Toyota main agent for a new key. They tried to code it but had problems and they gave up after trying. I bought the uncoded key from them but although it will turn the starter motor, the engine does not start. The only solution I can think is to bypass the circuit in the immobiliser unit which cuts the electrics to the engine.
Does anyone have a circuit diagram or details of the wiring which enables the code from the key to suit the immobiliser?
As I only have the one working key I am concerned that if I damage the immobiliser unit I may not get the car started again, even with the original coded key
I'm Shantal and I'm a moderator for this topic.
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Customer: replied 3 years ago.

I still need an answer if someone can find it.

I have looked on the internet and someone has posted a video on youtube showing how he solved a similar problem. However, his answer was to remove the immobiliser unit competely and then link 2 terminals on the socket which had the immobiliser plugged in.

However, I see this as a last resort and would only be attempted if I lost the one working key. To do this now may result in neither of the keys working if I get the linking wrong.It may also stop the alarm and door locking functions from working.

Do you not have an auto-electrician who has had experience with this immobiliser unit? It seems to be a standard fitment on all previas from 1990 to 2000 at least.

The solution is not urgent as I still have one working key, so you can take some time to find someone who can answer.

Please try to find someone.

Thank you


Hello Alan,
Thank you for getting back to me and providing more information. We will continue to look for a Professional to assist you.
However, should you wish to close your question and reverse your charges at any time please let me know.
Thank you for your patience,
Hello and Welcome..

MY name is ***** ***** Im happy to advise.

The first thing to say is, Toyota's are the worst when it comes to these key issues such as you have.. Generally and with the newer ones, if you lose your keys you have to have the whole system replaced - which costs a lot ! There is the way of bypassing that you have come across on the net / video.. Ive actually seen that - and it does work - your two keys would both work - because you have bypassed the signal system - so it doesnt ask for the signal from the key - either key.

Im afraid there are no published wiring diagrams for the security system on the vehicle- but all you would be doing anyway would be to look to bypass the system as you have seen above anyway... What you have there is either a faulty key - albeit new - it does happen..or, a faulty security immobiler unit... It has to be one or the other if a key will not program into the system.

So you are not a lot further forward Im afraid except to say you now know whats going on / how it works and so on... Personally with that , I would suggest to carry on as you are...and IF you should ever lose your key, you can go ahead with the bypass - Any good auto electrician can do that for you in half an hour or so.

Im sorry its not a straightforward situation but I hope that fully explains the situation you have there -

Im very pleased to have helped you - Do let me know if you need anything more --

*** Meanwhile - - >>>> Please do click on the "OK/ Excellent ratings" for me - Thank you in advance for that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Kind Rgds, MIKE.
Mike, Toyota Mechanic
Category: Toyota
Satisfied Customers: 39198
Experience: Tech Expert
Mike and other Toyota Specialists are ready to help you
Customer: replied 3 years ago.

Hi Mike

I rated you excellent, but I have not tried the solution - and will not unless the working key gets lost (I am looking after it well so I may never need to bypass the immobiliser.) Perhaps you could advise me if I need to implement the solution whether I should remove the unit completely and simply link the yellow wire to the next-to-last socket as per the youtube video, or leave the unit still connected and link those 2 wires. Does the immobiliser unit also control the central locking which currently works OK using the separate wireless "clicker"?- and if I remove the unit completely will that stop the central locking from working?

I would appreciate an answer if you have one - or I will have to try with and without the unit connected if the need arises.