Immobilizer Compatability from year to year

[particlewave]

Before doing that, contact forum member Qmulus. He knows his stuff and can probably fix what ECU doctors said was not fixable.
Unless the EEPROM was somehow damaged, Qmulus can fix it.

[TNT79Bronco]

Thank you. I have already done that. I wanted to get this information as well. Plan A and Plan B

[itsnotanova]

Any 97-99 set will work. You can even make the 531 work in a 535 (or vice-versa)car by modifying the harness connection. All you have to do is shave off that little tab that keeps it from sliding in.