One problem related to speed sensor has been reported for the 2003 Toyota Matrix. The most recently reported issues are listed below.
Abs, brake, & service engine lights came on. Took it to midas, they replaced speed sensors. When I got car back it shifted gears (automatic) funny & hesitated significantly shifting from 2nd to 3rd. Immediately returned car to midas. They re-diagnosed & suggested I take it to Toyota dealer (john elway's crown Toyota). They said it was speedometer cluster & replaced it which did not resolve my problem so declined to pay & asked them to put back my old speedometer cluster. They didn't & didn't charge me for the new one. Had car towed back to midas. They disconnected speed sensors & told me it was drivable. Got on freeway next day & car wouldn't shift from 3rd to 4th gear, engine revved to 6000 rpms, got off freeway & called midas corporate to complain. They said they would have franchise owner call me. He called but did not identify himself as the person I originated dealt with at midas shop, I know this because I called the number they called from & it was the midas shop. Went to midas, today (8/27/10), they asked me to bring car in tomorrow & they would put back old speed sensors & see what happens. They think it's the car's computer but in the meantime I'm out a thousand dollars.