How to Tune a Saab Viggen ECU

Written by brad swain
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How to Tune a Saab Viggen ECU
Reflashing the factory ECU can unlock up to 40 horsepower. (circuit imprime 2 image by daniel sainthorant from

The Saab Viggen was named after a Swedish fighter-jet made by the same company. It was released in 1999 as Saab's 9-3 flagship model. It came with a 2.3-litre turbocharged engine that made 230 brake horsepower.

The Viggen was marketed to driving enthusiasts but the Trionic 7 engine management system was designed with the layman in mind. With a simple guide, the right tools and an aftermarket Engine Control Unit (ECU) tuner the driving enthusiast can unlock up to 40 horsepower just by reprogramming the factory software.

Skill level:

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Things you need

  • BSR aftermarket ECU tuner
  • Socket wrench
  • 10mm socket tip
  • Adjustable wrench

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  1. 1

    Set the emergency hand brake, remove the key from the ignition switch and open the bonnet.

  2. 2

    Disconnect the negative battery lead from the battery terminal with an adjustable wrench to prevent any possibility of shock. This lead is usually black.

  3. 3

    Open the passenger's side door and remove the floor mat.

  1. 1

    Open the passenger's side door.

  2. 2

    Locate the screw holding the lower portion of the dashboard and carpeting in place. The screw is located across from where the speaker would be if the door were closed. Remove the screw with the 10mm socket wrench.

  3. 3

    Pull back the carpeting 10 to 12 inches. Do not crease the carpeting. The ECU, a silver box with a black and red plastic handle mounted under the dash, will now be exposed.

  4. 4

    Release the wiring harness coupler by pulling down the black plastic handle. Disconnect the wiring harness from the ECU.

  5. 5

    Plug in the BSR tuning computer and follow the instructions on the computer's screen. When instructed, disconnect the turning computer.

  1. 1

    Plug the wiring harness back into the ECU. Fasten the wiring harness coupler by sliding the black plastic handle back into its closed position.

  2. 2

    Fold the carpeting back into its original position. Replace the screw that holds the lower dash and carpet in place.

  3. 3

    Reconnect the battery and close the bonnet.

  4. 4

    Turn on the car and check to see everything is working properly. The car will not start if the reprogramming was unsuccessful.

  5. 5

    Take the car for a test drive. Start at slow speeds and gradually work up to higher speeds.

Tips and warnings

  • BSR recommends replacing the factory exhaust system from the catalytic converter to the muffler with an exhaust system that is 2 1/2 inch in diameter before tuning the Viggen software.
  • Most tuning companies recommend using fuel rated at or above an 89-octane content level and synthetic motor oil after upgrading the ECU in a Saab.
  • Installing aftermarket software will usually void any existing warranty on your vehicle.
  • New ECU software needs time to "learn" the most effective way to mix fuel and air in your car. The vehicle may jerk slightly under heavy acceleration. This is normal and should correct itself after a few days of driving.

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