Where is the ECU located on a 1997 Volvo 850?

Open up the engine hood, as you look at the engine from the front to rear, look over to your left. It will be in the black ABS plastic box, with a snorkel going to the front radiator. When you open this box, there will be 2 metal boxes inside; one will be marked Aisin, the other Bosch. The Aisin box is the transmission computer, the other is the engine. Hope this helps you out.