In 1999, Saab introduced its new upscale model, the Saab 9-5, to replace its predecessor, the Saab 9000. The 9-5 featured a redesigned body, more horsepower and torque, and an updated interior.
But the 9-5 is designed with the layman in mind. There are many aftermarket options to increase horsepower and torque in the 9-5. Some are more complex than others. By replacing the software or the Engine Control Unit (ECU for short), driving enthusiasts can unlock the horsepower and torque that the 2.3 liter turbo-charged engine is capable of of making, without having to change any of the car's hardware.
Set the hand brake, remove the key from the ignition switch, and open the hood.
Disconnect the negative battery lead from the battery terminal, using the adjustable wrench. Usually this lead is black. This will prevent any possibility of shock or shorting during the project.
Clear away any debris that has collected on the plastic run-off cover at the bottom of the windshield.
Loosen the plastic run-off cover by unscrewing the bolts that hold it in place with a Phillips-head screw driver.
Lift up the plastic run-off cover approximately six to eight inches, but do not remove it. Locate the ECU's oval-shaped plastic protective cover. The cover will have a plastic tube full of wires connected to its side.
Unscrew the bolts holding the protective cover in place using the 10 mm socket wrench. The socket-wrench extender may be needed to reach some of the bolts.
Lift up the black lever that releases the wiring coupler on the top of the ECU. The ECU is the silver box mounted vertically under the plastic protector. Disconnect the wiring coupler from the ECU.
Unscrew the two bolts located on either side of the ECU using the 10 mm wrench and slide the ECU out of its retaining bracket
Slide the new aftermarket ECU into the bracket where the factory ECU was just removed.
Replace the two bolts that hold the ECU in the bracket, using the 10 mm socket wrench.
Align the wiring coupler with the new ECU and plug it in. Fold down the black plastic handle to secure the connection.
Replace the ECU's plastic protective cover and the plastic run-off cover.
Reconnect the negative battery lead and test to see that the ECU is functioning properly by starting the car. The car is governed by the ECU and will not start if there is something wrong with the installation.
Close the hood and take the car for a test drive. Drive slowly at first to make sure the car is operating properly, then gradually increase overall speed and acceleration.
