size comparison of transponder chip inside the car key

Toyota Corolla Immobilizer

This article was made as a companion for the Toyota Corolla Immobilizer Reset Service we offer for the 2005-2007 Toyota Corolla, but it could also be helpful for you if you own one of those models and recently replaced the ECM with a used or recycled one and your car is not starting.

When you replace the ECM of these Corolla models and the replacement ECM is not brand new or at least was not previously reprogrammed, the engine won’t start because the used part has in memory the old key codes of the keys from the donor car. Those codes will not match the codes of your keys and will create a no-start situation.

Identifying the situation

Please note that with “no-start“, I mean that it cranks ok (the starter motor runs), but the engine does not start. If instead, the starter motor does not run either, then the problem is not the immobilizer and could possibly be an aftermarket alarm system that comes with many of these Corollas. The rule is; an immobilizer problem will cut injection and/or ignition but will let the starter motor crank. A problem with the anti-theft security system (alarm) will cut the starter too. If the problem seems to be the alarm, We are providing some instructions for that situation too under the heading “The Alarm system” further below on this article.

Your car may include one or both of the following:

  1. Immobilizer system (factory installed): Disables injection and/or ignition by internal means (ECM)
  2. Alarm / Anti-theft system (aftermarket installed): Disables starter. May disable injection and/or ignition by external means (Wiring).

What to do (immobilizer)

Ok, the ECM was replaced and the car won’t start? We have two possible solutions here. You may either; (1) perform an immobilizer synchronization (sync from now on) between the replacement ECM and the immobilizer system of your Corolla or, (2) if that does not solve the problem, you may use our corolla immobiliser reprogram service to reprogram the immobilizer of the replacement ECM.

The first solution above (sync process) may fail to do the trick if; (1) the memory chip in the ECM where the key codes are stored is full (it has a limit on how many key codes can be registered), (2) the memory chip is defective or damaged or (3) the ECM is damaged.

The good news is that the first solution (sync process) is free and most of the time it solves the problem and even when it sounds kinda complicated, it is a very easy to do procedure, and you can do it yourself with just a bare paper clip. It is explained in detail below.


The Sync Process (Free, Do it yourself)

To sync your replacement ECM with your car’s immobilizer system you will need to jump two connections in the OBD diagnostic port terminal for 30 minutes with the car key in the “ON” position. That is, all the way forward, right before starting the engine.

Because the ignition and all systems will be turned on, but the engine will not be running, you need to make sure that your car’s battery is fully charged or you must connect a charger to the battery while doing the sync process to ensure that voltage will not drop. If the voltage drops considerably (below 12 volts), the process must be restarted all over again and wait another 30 minutes. Also, it is important that if you are going to connect a charger, it must not be in “trickle” mode and it must be of good quality in order to avoid electronic noise from the charger that can negatively affect the sync process. If you do not have such a charger, then it is recommended that you fully charge your car’s battery first with any charger and then do the sync process, but do not use the charger WHILE doing the process.


A) First, locate the diagnostic port. It is under the dash in the driver’s side under the steering wheel, near the hood release lever. It is a dual-line 16-pin connector (8+8). See the illustrations below as reference.

Pinout of the OBD port

OBD Port location


B) Now, with the engine off and the keys in “off” position,  jump connectors #4 and #13 of the diagnostic port by using a bare paper clip. Below are example illustrations.

Jumping the pins 4 and 5 of the OBD port 1

Jumping the pins 4 and 5 of the OBD port 2


C) Next, with the paper clip in place, turn the key all the way forward to “on” position (ignition on) right before engaging the starter and leave it there for 30 minutes.

Different lights in the dash panel will start flashing. This is an indication of the process going as expected. If lights don’t flash, then something is not working as expected and you should start over. This not happening as expected can be caused by a poor electrical connection in the jumper you made or if jumping the incorrect connections of the OBD-II diagnostic port terminal. Make sure you are using connection #4 and #13 as instructed previously before proceeding. Below is an animated GIF of what it should look like when it is working correctly, so you can have an idea.


Dashboard flashing random lights when doing sync


D) After 30 minutes, turn the key to “off” position and remove the paper clip from the diagnostic port. After removing the paper clip, you may attempt starting the engine. It should start at this point if the ECM and everything else is good. If it does not start, you may send us your unit so we can program it.

The Alarm system

If the problem is that the starter motor is not running (not cranking), but all electrical systems seem to be right and the battery is charged, then you should try to reset any aftermarket alarm or anti-theft system if any (not to be confused with the immobilizer system). The ECM, good or not, will not prevent the starter from engaging. The immobilizer system will disable injection and/or ignition, but not the starter. So if the engine is not cranking when you try to start the car, it is not necessarily the ECM or the immobilizer system in most cases.

What happens in most cases is that any aftermarket alarm or anti-theft system will need to be reset if the car battery is disconnected longer than a specific time, usually in minutes. In those cases, it is this aftermarket security system that is disabling the starter.

Some Corolla models come with a security light that serves as an indicator and it is a button at the same time. Below is an example illustration:


Corolla security light


In most cases, to reset the alarm you may try arming and disarming it with the remote control provided for it (key fob). If that does not work, then try the following:

1 – Insert the key and turn it to on position, but do not start the engine.
2 – Push the red security button (picture above) twice.
3 – Now start the engine.



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