2000 Volvo S70 The abs and check engine lights are on

The red brake light comes on and the speedometer quits working. The brake light will go off and the speedometer will still not work. The car will start to stall when you turn a corner sometimes with the brake light on and sometimes with the brake light off. The transmission will sometimes go into neutral or slip when you go up a hill, and then sometimes it will not shift into reverse when you stop with or without the brake light on. The speedometer will just quit working. The transmission will stop shifting with or without the brake light on. I've spent the money to do a tune up, clean the injectors, check the transmission and the brakes, and it just keeps doing these strange things. Any ideas?