Toyota Corolla Immobilizer
We have heard a lot of customer complaints about the built in immobilizer on the 2005 – 2008 Toyota Corolla, being the most common complaints; “The car cranks OK, but won’t start” or “The car cranks and starts, but the engine die in about a second”.
The problem in most of the cases is caused by the immobilizer system, either by a malfunction or by a code mismatch between the key and the ECM.
The immobilizer is an anti-theft system implemented on many modern cars and it is integrated by (1) the ECM, (2) the car keys (called “transponder keys”), (3) a coil antenna mounted around and inside the key lock assembly for communicating with the key internal circuit and in some models, (4) the transponder ECU, which processes signals of this system. This last one is not always included. In some models, the job is done in the ECM and there is no transponder ECU present.
Inside your car key’s plastic handle, there is a micro chip in a glass or plastic capsule which contains the whole circuit needed for the key to transmit an unique code when it is close to the energized coil antenna inside the key lock. That is why the key’s handle is wider than normal.
Many crystal transponder chips:
The circuit inside the key needs no battery, as it is powered up by inductance by the magnetic signal coming out from the coil antenna. Right after the key is energized by the antenna signal, it transmits a response to the coil with the code it has stored in its internal memory. All the communication and power feeding between the car key and the transponder system is electro-magnetic.
Transponder antenna (inside key lock cylinder):
The code received by the coil antenna from the car key, is amplified and decoded by the transponder circuit and then transmitted to the ECM to be compared with the code already stored on its memory. If the comparison tests Ok, then the transponder circuit sends a signal to the ecu to allow the engine to run. Otherwise, the ECM will not send any signal to the injectors and igniters.
There are several cases where you may have some trouble with the immobilizer.
1. In the event that the owner loose a key, he or she can order a blank key, have it cut and programmed by a locksmith by using a key cloning equipment.
2. If all keys are lost, then the ECM must be reprogrammed (sometimes erroneously called flashing or reflashing) to accept new keys from zero.
3. If the ECM is replaced by an used ECM, the keys in the used ECM memory will not match the keys you have and the engine won’t start. The solution in #2 above will work flawlessly, but in this case, you may try doing an immobilizer synchronization to match the incoming ECM to the immobilizer system of your car before you invest any money and time on this. The solution is below, but if it does not work, as sometimes it does not for no reason, then the solution #2 above will always work instantly.
To sync your replacement ECM, you will need to jump two wires in the diagnostic connector for 30 minutes, with the key in “ON” position, that is, all the way forward right before starting the engine. because of this, you will need to make sure that car battery is charged completely or you may do the sync with a charger connected to the battery to ensure that voltage will not drop. If voltage drops too much, the whole process must be restarted and the 30 minutes wait will need to be waited up again from zero.
Important: If using the service in solution #2, please note that the VIN number will be erased as a normal automatic process, done internally by the ECM after clearing or resetting the immobilizer data. It can not be avoided if resetting the immobilizer, but it will cause no performance problems or problems of any kind, except for having the check engine light on, indicating that the VIN number is missing. The VIN can be entered by bringing the car to a Toyota dealer or any independent shop that has the equipment to do so. It can be done with any J2534 capable scanner or device, with the Toyota VIN update software.
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