My vehicle did not start after I installed a used ECM I bought on Ebay. The vehicle starts fine with my old ECM.

Should I have the used ECM flashed at the dealership or is the used ECM malfunctional? I own a Saturn Ion 2003.

  • 3
    I forget if you have to write the VIN to your new PCM or not, I believe you do. You also need to do a pass lock relearn. – Ben Dec 16 '16 at 2:16
  • Ions didn't have chip keys for that model year. – tlhIngan Dec 16 '16 at 5:52
  • Is the security light (lock symbol) on the dash turned on? – 3Dave Dec 16 '16 at 21:02

There are steps to replacing an ECU. Find detailed instructions here.


  1. Disconnect the battery and let the car sit for 15 minutes.
  2. Plug the new ECU in, reconnect the battery and turn the key to "accessory" or "on", whatever turns all your warning lights on. Your Check Engine Light needs to be on at this stage or your ECU is defective.
  3. Let the car sit like this for 5 minutes with the engine off and the Check Engine Light on.
  4. Turn the key to off, then start the car.
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Make sure your battery is pushing out at least 12 volts before doing anything. I would take it out and charge it fully first while installing the new ECM computer.

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