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Toyota Corolla Immobilizer

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We have heard a lot of customer complaints about the built in immobilizer on the 2005 – 2006 Toyota Corolla, being the most common ones “The car cranks OK, but won’t start” or “The car cranks and starts, but the engine die in about a second and a half”.

Size Comparisson of the Transponder Chip inside the Toyota Car Key

Well, the above is most of the times caused by a mismatch of the engine immobilizer or a malfunctioning of its circuit (very rare).

What is it?

The immobilizer is an anti-theft measure, implemented on many modern cars today.

The system is integrated by (1) a special circuit in the ecu, (2) the car key, called “transponder key”, and (3) a coil antenna mounted around and inside the key lock assembly and (4)¬†the transponder circuit, where the antenna connects.

Inside your car¬†key, in the black or grey plastic part, there is a micro chip in a glass capsule, which contains the whole circuit needed for the key to transmit an unique code when close to the energized coil antenna. That is why your car key’s¬†plastic part is wider than normal, to accommodate the device.

The circuit inside the key needs no battery, as it is powered up by magnetic signals out coming from the coil antenna. Right after the key is energized by the antenna, it starts emitting back to the coil, the code it has previously stored. All the communication and power feeding between the car key and the transponder circuit installed inside the steering column, is electro-magnetical. The code that the car key has programmed inside, is the code given to it when it was programmed by the dealer, using part of the VIN number.

The code received by the coil antenna from the car key, is amplified and decoded by the transponder circuit and then transmitted to the ecu to be compared with the code already stored on it and then be sent back to the transponder for comparisons.

If the comparison tests Ok, then the transponder circuit sends a signal to the ecu to allow the engine to run. If on the other hand, the code is not recognized (mismatched), the ecu shuts off the engine a second and a half after starting it and flash the security indicator on the dash board.

Why this happens?

Well, this can be caused by several reasons. Some are the following:

1 – The owner lost a key, ordered a new one, but since the code is unique to every key, it won’t match the one on the ecu and will fail the comparison test, shutting the engine down.¬†On this state, the car should run with the valet parking key or any other valid copy of the key¬†the owner may have. The problem is if the lost key was the only one available.

2 – The owner needed an ecu replacement for any reason and the same will happen here, the code in the ecu won’t match the one on the key, shutting down the engine.

3 – A sudden malfunction of the system caused by an unexplainable reason like a power failure or by connecting an incompatible, wrong or faulty scanner or diagnostic equipment or anything alike.

What to do?

We have, as told by the dealer, 3 options here.

1 – Go to the dealer so they cut a new key and synchronize it (program it) with the existing ecu. The ecu must be in a state that can accept new keys. All ecru’s are supposed to have a capacity of accepting from 8 to 10 new keys (maybe around $100).

2 – If the dealer has the equipment, the ecu must be re-seeded so it can accept new keys, in case number one above doesn’t work (even more $$$).

3- Replace the ecu for a new one if the above two options don’t work and possibly¬†will need to buy new blank¬†keys. (probably from $800 to $1300).

Too pricey

yes, it is too pricey, but there is a third option not offered by the dealers, probably because they don’t know it. The ecu can be reflashed (reprogrammed) so it will be ready to accept either new or old keys. This procedure will put the ecu key memory in a virgin state,¬†as a new one. The downside of this is that a special reprogramming equipment and software is needed, but we¬†have tested it and works¬†perfect and only takes a few minutes. Another downside is that the ecu must be sent by mail so the job get done.

What is done to the ecu? It is reprogrammed (only the part that works with the key codes) without removing any part from the circuit. The job is completely untraceable and warrantied to work 100%.

This service can be found at the link below:


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February 24, 2009

It was interesting to find this article as I just recently purchased a used 2006 corolla and was only given one master key. This is the only key I have for this car and they did not give me the code. Can a dealer still make another master for me (using the one I have) even if I don’t have the code?

PostedbyAndrea Bailes
February 24, 2009

Hello Andrea. Thanks for writing.

Yes, the dealer should be able to make a new key with your master and the car’s VIN number. The problem for the dealer is when the master key is lost.

The VIN number of the car, the pin number (seed) and key codes are stored in the ecu (car computer). In case that the master key is lost, then the ecu must be reset (as explained in the article above) for it to learn new keys.

March 21, 2009

I just received the Toyota ecu you serviced this week. Now it works fine with my keys. Just wanted to thank you. I saved a lot as the dealer quoted a lot of $$$. About the issue that we were talking about, with the check engine because of the VIN number, I went to the dealer and they set it for free as you adviced to do. I will promote your service (as I am doing now) here in my area. Thank you very much!

PostedbyDaniel Soto
March 21, 2009

I am glad you brought your car back to life. It was a pleasure helping you.


April 21, 2009

My father bought a Toyota Corolla 2006 S model two years ago from US. He got only one master key with remote controller.
He¬īs living at Slovakia and wants to make an duplicate key but our dealer of Toyota said him that they have no software for programing of this key which is needed for Toyota from US. Because cars from US market are different than cars from European market. Further more at Toyota Slovakia they told him “there is exists some instructions for self-programming of this key.” Could you advice me if instructions like this does exist or what can he do when he wants to get this key.

P.S. if it is possible to self-program the key and u have the instrustions could u send me them. Thank you


April 23, 2009

Hello Jan.

About the keys from USA being different from the European ones is true. Codes change.

About programming a new key, it is easy and simple, provided that you have (1) an USA key of your model and (2) the key is blank and unused.

You can do this procedure either before or after mechanically cutting the key.

You might want to revise and practice the procedure before actually doing it, as it have a few steps that each one have a specific time frame.

It is a s follows:

1 Take the master key you have and insert it into the ignition switch. The master key should be black colored, not grey.

2 Turn the key to on position and before 15 seconds, press and release the accelerator pedal for exactly 5 times.

3 Now, before 20 seconds, press and release brake pedal for exactly 6 times.

4 At this time you can remove the master key and within 10 seconds, you must insert the new black key to be programmed into the ignition switch.

5 Next, before 10 seconds, press and release the accelerator pedal just once.

6 Wait a few seconds, then remove the new programmed master key.

If you want to program another new key, you must insert it in the ignition cylinder within 10 seconds after the above procedure and press and release the accelerator pedal only once and wait a few seconds before removing it.

Test all the keys you programmed after finishing.

You can program up to 7 keys using this method. After that, the ecu must be cleared to accept new keys.

Best regards.

April 23, 2009

Hi admin.

Thank u for your response a for the instructions. That is the matter what I want to ask you.
I found some instructions before you sent me yours on

Add Duplicate Key:

1. Simultaneously depress and release brake and accelerator pedals 1 time.

2. Insert existing master key into ignition. Do not turn the key from the OFF (LOCK) position.

3. Within 15 seconds of inserting the key, depress and release the accelerator pedal five times.

4. Within 20 seconds of completing the above step, depress and release the brake pedal six times and
remove the key.

5. Within 10 seconds, insert the new key into the ignition.

6. Within 10 seconds, depress and release the accelerator pedal one time.

7. After 80 seconds the new key is registered and the security light will go off.

8. Remove new key and depress and release the brake pedal 1 time.

Steps 2-7 are completly the same like yours steps (1-6). But step 2 (in my instructions) is different in position of master key.

So which position of master key is correct and should be done the steps 1 and 8 (in my instruction) as well? Because my father already did whole process according to steps above but nothing happend and master key was in OFF(LOCK) position.

And secondly: I was reading on forum of toyota that during the self-programing can program get frozen and ecu have to be replace. Is that right???

P.S. I hope that your instructions will be work.

April 24, 2009

Jan, we have done it with the key in accessory/radio, not on ignition position, so I guess that for the process being taking place, it will be the same as ignition circuits will be powered off. Depressing both pedals might be some type of reset before entering the programming/erasing mode. Ours, worked OK without that step.

I recommend that you first try the all key erasing method, as you only have one key, then do the steps to try to program the new one.

If still nothing happens after trying both instructions (here and the mentioned site), then it might be the case that (1) the key being tried to program is not compatible with the transponder on your car or (2) for some unknown reason, your ecu is not accepting any more keys even after the process of erasing all keys.

It is important to notice the flashes of the security lamp, as per the instructions in the site you posted above, as a guide for knowing if the process is being working. If for some reason it doesn’t flash as expected, something is wrong, either with the ecu or the new key.

I assume that the car is working with the unique key you have, so I rule out the rest of the circuits like the ring antenna and the key lock transponder circuit.

About dealers, they usually replace the ecu if they don’t have the equipment for resetting the ecu. We do reset the ecu with an eeprom programmer and the correct file for writing on the security chip, which is located in the ecu circuit. A little bit of a technical job.

April 14, 2010

buen dia ya veo que tienen amplia experiencia com la materia y queria pedirles asesoria.tengo un toyota corolla 2006 y suplante la ecu el inmo y las llaves todo nuevo de caja. programe las llaves y todo bien el carro prendio perfecto. pero tengo un codigo p0630 que me dice que el vin no ha sido programado .cual es el procedimiento para este caso y como se realiza con el tester inteligente gracias..

Postedbydarwinl eal
April 14, 2010

Hello Darwinl.

That will always happen when you replace the Corolla ecu for a new one. The new ecu does not have the VIN number on its memory, so it will have to be entered on a certified dealer or using a Toyota specific application with the capability of entering the VIN number, like Techstream. That’s a common issue when replacing the ecu, but there is no malfunction at all.

If you don’t do it right away, don’t worry, as the check engine light and P0630 will be all to it. Apart from that, all systems, including the immobilizer will be working ok. You won’t have any problem. When you have any spare time, you can go to a dealer near you to enter the VIN number. In some dealers it is a free job, while in some others they will charge a small fee about $40.00 – $50.00. It will all depend on the dealer, but it is a 15 minutes job.

Best regards,


June 9, 2015

I had immobiliser in my 96 corolla 4afe removed,it was starting okay for a while now the ecu light does not go on and the car just cranks but won’t start.What could have gone wrong?The ecu looks ok, Somebody please help,I’m at wits end

June 9, 2015

Hello Kabelo.

Thank you for writing ūüôā

After the immobilizer was removed, for how much time did it start ok before the ECU light went on and stopped starting?

I wonder how did the immobilizer was removed. In all Toyota models I have seen, the immobilizer can be reset or can be reprogrammed, so it does not look for transponder keys, but it is never completely removed. There is always a code working on the immo chip.

If it was the second option above, then the key amplifier (ring antenna circuit in the key cylinder) must be disconnected and if a separate immobilizer box, known as immobox or transponder ecu, it must also be disconnected.

I reprogrammed once a 1998 Toyota Camry so it does not look for transponder keys and it worked fine the whole day. Next morning, it did not want to start. After the key antenna amplifier was disconnected, everything was working fine again. In this case, the immobox was not present.

June 16, 2015

thank you very helpful,but my car 2005 corolla ce does not set alarm,neither security light flashes or stay on when not set(disarm)it is off,please sr our family need your expertise

Postedbysoon jung
July 9, 2015

changed my starter motor on my 1998 corolla but the problem was a worn barrel so got new set from brakers ie immobleiser key barrel now car will not read turns on but will not fire

November 10, 2015

Just replaced ECU(used)on 02 Corolla Runx,engine cranks but doesn’t start, security light flashes, can anyone please help, How can i bypass the immobilizer to kill the security feature so it wont search for the transpondent key.

many thanks for any assistance.

PostedbyMace AP
November 10, 2015

You will need the ECM to someone that can reprogram the ECM to accept the keys. A Toyota dealer should be able to do it.

One thing you may try your self is a trick for synchronizing the used ECM with the key codes in the immobilizer system. The picture below describes it. Take in account that the vehicle battery must be fully charged or connected to a boost charger, because the process takes almost half an hour with the car switched to “run” position and the engine off, which will drain a weak battery. If the process is interrupted even slightly because of low battery, it must be started over and wait 30 minutes more again. So please make sure about battery charge.



Toyota immobilizer key synchronization process

December 29, 2015

Regarding this issue, I have something that’s a variation to this issue….my wife’s friend has a 05 Corolla that has a
intermittent starting issue.
-key in ignition (black key)all lights work, radio, ect. but motor will NOT crank at all, lights do not dim, so it’s not a Battery or Alternator issue as their family mechanic said the electrical system checks out perfectly.
She had heard to cycle the Key On Key Off 5 times and it would work and still is intermitten, can you help?

PostedbyJason Gallardo
December 29, 2015

Hello Jason.

Does the car has an alarm that cuts starter? That is mostly the problem in these cases, as the immobilizer disables ignition and injection, but do not disable the starter at all. With the immobilizer set, the car will crank until depleting the car’s battery, but the engine will not start.

Your problem must be in an aftermarket security system (alarm) that could be installed in the car or in the starting circuit wiring per se.

If the security system is the case, try resetting it. If that does not work, you should search for defective components in that system.

If no security system, then you should check the starting circuit components with the provided diagram in the link below. It is composed of the starter itself, some relays, some fuses, its wiring and the ignition switch, which reminds me, that a defective ignition switch tends to do that problem too.

I hope this helps,



2005 Toyota Corolla Starting Diagram:

December 30, 2015

ok Richard, I have some more info from last night and her car.
It does in fact have a Factory Installed Toyota alarm.

She said that when the corolla decides it’s not going to start:
– all the lights, radio work
– when she turns the key, NOTHING happens as in: No engine rotation, no lights dimming.

AAA tow truck driver shows up and she says “he tapped on something right above the starter” and the car started, so he left….as I was driving home the car completely shut off and I called AAA again and they towed me home. Same issue as all the lights and radio worked, but the motor wouldn’t rotate when I turned the key”

In my honest opinion, regardless of what their mechanic had said about the electrical being 100% ok, this seems to be leaning towards a “Starter” or “Starter Solenoid” issue? Yet, why would the car shut off while she was driving???

PostedbyJason Gallardo
December 30, 2015

Exactly my thoughts. The starter may be intermittent, but it won’t make the car to shut off by itself.

If it would only be a starting problem, I would say it is the starter itself, but more commonly, the ignition switch.

But, since the car is shutting off by itself, the problem seems more to be in the security system. Those systems normally send an ignition off signal, along with a starter cut off signal when triggered. If it is so, triggering the security system could be caused by a malfunction in the system itself or intermittent wiring. Reminds me the systems that turns the car off after a few minutes if it is hijacked.

October 18, 2016

Having problem with 2010 corolla. Currently at local mechanic and he thinks the after market remote starter is messing it up. Car turns over fine just will not start. Has engine immobilizer indicted in code. Don’t get how this just happened as I have the original keys. He is going to start ripping out remote starter. Please help, there has got to be away to reset something easily doesn’t there?

October 20, 2016

Hi, I have a 2002 Toyota Celica. ECU was changed previously. Car starts but cuts off after a second or so.

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