MAT Sensor

First post here, so thanks in advance for the replies. The service engine soon light came on in my 91 Eighty Eight. After pulling the diagnostic code, found that the MAT sensor was bad. I replaced the sensor and the service engine light was still on. I removed the negative battery terminal and replaced it after waiting for about 10 minutes, the light is still on. I checked the resistance on the old sesor, which was about 1330 Ohm, the resistance dropped rapidly when I heated the sensor with a hair dryer. Any susggestions as to what the problem may be, I'm not convinced that the sensor was bad after all.