Simple Immobilizer SMD EEPROM Removal and replacement



When you replace your 2001, 2002 or 2003 Toyota RAV4 ECM (car computer or engine computer) with an used unit, either bought at eBay or at a salvage yard, junker, etc., if your vehicle is equipped with an immobilizer system, which is an anti-theft security system, you must either reprogram the ecm to work with your existing keys, or buy new keys, which must be cut and programmed for matching the ECM unit you just purchased.

In this article, we will cover the part where the ECM is reprogrammed, as that is the easier way, and will use as an example the 89661-42820 RAV4 ECM. That part number is to mention just one, as this procedure will cover all 2001 – 2003 models, either 4×2 or 4×4 wheel drive.

For reprogramming, if you have an EEPROM programmer, you can do the programming either in circuit or off circuit by using a reset file. You may get the immobilizer reset file for download at:

2001-2003 Toyota Immobilizer Reset file Download

NOTE: The above product is ONLY for ECMs using the immobilizer option.

You may check the following article if you which to do the programming “in-circuit”:

Reading and Writing Immobilizer EEPROMs in circuit

For doing it off circuit, you will need to remove the EEPROM chip, reprogram it and solder it back to the circuit.

If you DO NOT have an EEPROM programmer, but have electronic soldering skills, you may order the EEPROM chip already programmed and replace the original chip with it.

You will find the chip at Immobilizer Reset EEPROM. The Immobilizer Reset EEPROM is a chip (in this case a 25080 SPI EEPROM) already programmed with the immobilizer reset codes and after it is installed (soldered) in the ECM, it will put the ECM in auto-registration mode. It means that after installing the ECM back in the vehicle, it will register the first keys you use to start the engine. Those first keys should be your existing keys. Then, the vehicle will only start with those keys.

The EEPROM you will replace will have the markings “25080” on it and it is near one of the two existing micro-controllers. The reference in the circuit board will be “IC1003”. Below is a picture for easily locating the part.

In the picture above, you can see the location of the immobilizer EEPROM. Take note of the orientation of Pin#1, as the reset EEPROM must be installed the same way. For replacing the EEPROM, just unsolder the existing one, clean the copper traces from excess solder and solder the reset EEPROM in. Below is a simple method of doing it. There of course, are better methods, like using a heat gun or “ChipQuick”, but we are showing the less expensive way and assuming that you only have the soldering iron, as the other equipment is not current on a hobbyist tool box.

Cover with solder ALL 4 pins on each side of the EPROM. Make sure that solder gets in good contact with all 4 pins on each side of the chip. Use a soldering iron which is not more than 35 watts.

Hold the EEPROM with tweezers, while heating both sides simultaneously until it is loose. After the chip is loose, just pull it up with the tweezers, away from the circuit board. Avoid from getting molten solder in other areas of the circuit. If it does, remove it before you forget about it and power the ECM with it in the circuit. It can cause short circuits that can destroy the ECM beyond repairable.

Before soldering the Reset EEPROM in place, clean the circuit from excess soldering by using desoldering braid. That will also allow to accommodate the new Reset EEPROM in place more easily.

For soldering the Reset EEPROM, put it in place and hold it with a sharp pointed tool, while heating with the soldering iron one of the pins of the chip. That will temporarily lock in place the chip, while the other pins are soldered. Make sure that you are putting Pin #1 to the right place.

That’s it! After soldering all the 8 pins of the EEPROM chip, make sure that; again, pin #1 is pointing to the right direction, make sure that there is no soldering debris on any part of the circuit and make sure that you put the new (Reset) EEPROM and did not install back the same EEPROM you just took out without noticing 😉

Now is time to put your ECM back together and reinstall it in your RAV4. Put your key in the cylinder lock without turning it to any direction, wait 10 seconds and then start the engine. If everything was done right, it will start and run as normal.


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7 Responses

  1. sigfredo rivera says:

    for remover eeprom mazda 3 immobilizer in ecu you have picture?

  2. Shawn says:

    Hi good day I lost my key from my VW Golf Mk1 1.4i 99mdl it uses a transponder key how do I read the 4 digit pin using Carprog I also have a T300 plus blue one but it also can’t read the pin code it only gives me the access code and the immo info The immo unit is Siemens and the chip inside is Motorola the only problem is I don’t have the diagram to soldier the pins with the A6 addapter

  3. Kipeli says:

    Location of immobiliser module on mazda axela 2006

  4. balanti adam says:

    halo please my problem is I have carprog and ad900 I want toturial and more explaination on how to programming eg golf,toyota,honda and the restplease even if its your forum I can visit and make sure I learn it very well thanks

  5. Luke Campbell says:

    If I buy a epprom for my 1999 Avalon do I just use the number on it to reference it or do I have to get one with programming in it ?

  6. Guest says:

    Hello Luke. You will need an eeprom with programming in it. Eeproms normally come empty. So you will either need an empty eeprom with the specific number (93C66, 94050, 24C56, etc.) and put the programming yourself via an eeprom programmer and the right file, or you will need an already programmed eeprom. Program in the eeprom must be the specific program for your vehicle.

  7. Maxima Eldridge says:

    Fantastic information posted! Really cool responses. Good job!

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