ajs1391

My 1997 ES 300 has been diagnosed as having a bad ECM. I have located a rebuilt ECM but I am unsure of whether it needs to be programmed with my VIN or not. Some discussion indicates immobilizer may not work without reprogramming. Any thoughts?

LeX2K

I think the immobilizer system started in 1998 for the ES but I could be wrong. Search Ebay for Lexus ECU reflash there are services that will reprogram the ECU that will be ready to accept new keys. But I'd contact them first if your car needs it done, also make sure to match the part number (or a change up number) of your ECU when replacing.

speedkar9

Wow how coincidental.

I am working on a hack for reprogramming the immobilizer in case of an ECU swap or lost keys on these older Toyota cars.

The immobilizer data is located on IC900, a 93C56 EEPROM chip inside your ECU. You need to either copy this information to the new ECU, or "virginize" the EEPROM to put the car into auto-programming mode where you can program new master keys.

I've got a working proof of concept for my car and will post up a video and DIY in another week or two.

LeX2K

Wow that will be awesome if you can pull it off. Could one simply swap the ROM from the old ECU to the replacement? Does the replacement ROM need some basic code before it is installed on the ECU? Or it goes in blank.

speedkar9

Yes, there are a few things you can do, you can swap chips (desolder), swap the program from one chip to the new one (copy and paste), or write a "Virgin dump" to the chip to put the car into auto-programming mode. The latter is used in a lost key scenario (which is my fundamental reason for investigating this, as I'm getting a lot of requests from people with only valet keys).

The virgin dump contains mostly zeros, but from my experimentation there are a few values that you have to keep in there to allow the computer to program all 3 keys.

The programming part isn't that hard and is pretty much the same procedure as my odometer programming project from 2 years ago.

DJPsystems

I have a 97 and I can tell you that this year does not have any immobilizer in the key. I believe that 98 was the first year for the immobilizer chip in the key.

LeX2K

Thanks for the info.