Replacing the ECU

After relaxing my arm and stuffing it in bit by bit, I was able remove the bracket bolt, unplug the connector, and remove the ECU. Steering column support shaped indentations in my arm chronicle my progress. The hardest part was getting the connector lined up and plugged into the new ECU.

Once the new Key Transponder ECU is installed, I attempt to register the first key. The way it’s supposed to work is — 1) install new ECU 2) put the first key to be registered into the ignition lock cylinder and turn the key to the on position 3) leave the key in the on position for 30 minutes. 4) start the car 5) use the new master key to register the other keys.

Unfortunately, this Prius had a bad 12 volt battery, and was unable to stay “on” for more than 5 minutes before going black. Those of you familiar with flashing ECUs may be wondering the same thing I wondered. What happens if the power goes out in the middle of programing? Is the new ECU now a paperweight? Only a new ECU can register a key without having a Master Key. Will an ECU halfway through its first registration still allow Master Key registration? Turns out a dead battery won’t mess anything up. Luckily for me. Next time, I’ll use a battery charger. It may not ruin the computer, but it is a real pain.