96 Geo Prizm camshaft sensor code. but I need help

I have a 96 Geo Prizm with the 1.6L. I replaced the timing belt on the car and about 200-300 miles later hte check engine light cam on. The coade said it was a cam shaft sensor, but these cars do not have a cmashaft sensor. I was told that the timing from the new belt must be off, well I just took it apart and the marks are right on. So can anyone help me?

Mark